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_reverseengineering.2547 | I have a SPANSION FL016KIF (pinout on p.12) on a board and I want to dump the data. I try to use the BusPirate v3 for that.I want to do this in-circuit. I didn't connect WP# and HOLD#.This is the command transcript I used to set it up (I also tried other variations):HiZ>m1. HiZ2. 1-WIRE3. UART4. I2C5. SPI6. 2WIRE7. 3WIRE8. LCD9. DIOx. exit(without change) (1)>5Set speed: 1. 30KHz 2. 125KHz 3. 250KHz 4. 1MHz(1)>3Clock polarity: 1. Idle low *default 2. Idle high(1)>1Output clock edge: 1. Idle to active 2. Active to idle *default(2)>2Input sample phase: 1. Middle *default 2. End(1)>1CS: 1. CS 2. /CS *default(2)>2Select output type: 1. Open drain (H=Hi-Z, L=GND) 2. Normal (H=3.3V, L=GND)(1)>2ReadySPI>WPower supplies ONAnd this is the instruction I try to execute, which should get some device information:SPI>[ 0x9f r:4]/CS ENABLEDWRITE: 0x9FREAD: 0x00 0x00 0x00 0x00/CS DISABLEDSPI>Unfortunately I only get zeros READ: 0x00 0x00 0x00 0x00. How can I figure out the correct settings for SPI? Are there other pitfalls? | Dump Flash Memory with SPI from SPANSION FL016KIF | hardware;spi | null |
_webmaster.86340 | I'm sure it is my mistake in mod_rewrite rules, but I can't seem to figure it out. I've set up the rules for my new site and all works perfect, unless - I try to create a sitemap. The URLs get duplicated/triplicated/etc... pretty much ten URLs which open the same page. Here are the rewrite rules: RewriteRule sport/training/article/(.*)$ ./article.php?q=$1RewriteRule sport/eating/article/(.*)$ ./article.php?q=$1RewriteRule sport/track/article/(.*)$ ./article.php?q=$1RewriteRule sport/training/(.*)$ ./list.php?l=1p=$1RewriteRule sport/eating/(.*)$ ./list.php?l=2&p=$1RewriteRule sport/track/(.*)$ ./list.php?l=3&p=$1When my site gets crawled, the result is something like this: http://www.blah.com/sport/training/article/article-about-sporthttp://www.blah.com/sport/training/sport/training/article/article-about-sportSometimes it is even like this: http://www.blah.com/sport/training/sport/training/article/article/article-about-sportAll of the above open the correct page BTW.Internal generated link structure design seems to be ok. What am I missing here? | After mod_rewrite the internal URLs are duplicated many times when crawling | mod rewrite;links;url rewriting;canonical url | I just figured it out. It actually turns out to be a mistake in URL generation. It was an idea about crawler sees what it sees that helped me to solve this. |
_unix.298517 | I'm not sure if my title is describing it correctly, but essentially, I was wondering if there was a way to register a callback with the system so that when a user attached an external drive my callback is called and I can then proceed to manually mount the disk.What I'm doing currently is putting a default entry into /etc/fstab with nofail on, this way if the drive is inserted before boot it will be automatically mounted. What'd I'd rather do though is allow the drive to be inserted at anytime, and have it automounted by the system. Is there a way to do this without polling lsblk in a loop? | Register callback for newly inserted disk? | mount;ext4;automounting | null |
_unix.83730 | I have a directory which contains a number of subdirs. Each of these subdirs again contains a number of subdirs (call them subsubdirs). Now I would like to count the average number of subsubdirs in the top level directory. | Average number of subdirs | files;directory | This script uses awk to extract sub-directories from the ls list. Each subdirectory is entered and it's subdirectories counted. Finally the average calculation uses dc. I've set dc (using 2 k) to output to 2 decimal places.dirs=$(ls -ld * | awk '$1 ~ /^d.*/ { print $9 }')ndirs=0for d in $dirsdo cd $d current_nsubdirs=$(ls -ld * 2>/dev/null | awk '$1 ~ /^d.*/ { print $9 }' | wc -l) nsubdirs=$(($nsubdirs + $current_nsubdirs)) ndirs=$(($ndirs + 1)) cd ..doneecho Total subdirs $ndirsecho Total subsubdirs $nsubdirsavg=$(dc <<< 2 k $nsubdirs $ndirs / p)echo Average subsubdirs $avg |
_softwareengineering.256037 | Google has an advanced diff tool specifically designed for compiled binaries called Courgette.Is there any reason why they wouldn't use this in Android and the Google Play Store to download updates? In my basic understanding of Java, it seems like it shouldn't be any more difficult (perhaps even easier?) to create 'diffs' like this because of Java's bytecode nature. Am I wrong? Are there any security reasons? Note: I know that unless someone from Google responds, we won't know for sure. But I'm asking for any obvious reasons - I'm an Android developer and sometimes get notes from people complaining about frequent updates, so it is somewhat relevant to me. :) | Why doesn't Google use Courgette for Android updates? | google;diff | null |
_unix.23120 | Since I removed rekonq from my system, numerous apps which launch links, e.g. Stackapplet and Thunderbird are not correctly launching links with Firefox, which I am using now as my primary browser.I need a global way of telling Kubuntu to automatically launch links inside apps with Firefox, I have tried changing file associations but that appears to be irrelevant. System Kubuntu 11.10 64-bit@rozcietrzewiacz - your suggested solution can be found here: | Broken link/launch behaviour on Kubuntu 11.10 desktop after rekonq uninstalled | desktop environment | null |
_softwareengineering.91230 | From Wikipedia:the term endian or endianness refers to the ordering of individually addressable sub-components within a longer data item as stored in external memory (or, sometimes, as sent on a serial connection). These sub-components are typically 16- or 32-bit words, 8-bit bytes, or even bits.I was wondering what addressable means? For example, in C, the smallest addressable is a byte/char. How can a bit be addressable?Thanks and regards! | Addressable memory unit | c;memory | How can a bit be addressable?The 8051/8052 family and some other microcontroller architectures (low and mid-range PIC, Infineon C16x/STM ST10) support bit-addressable addressing. In the 8051, the RAM bytes from 0x20 to 0x2f are bit addressable (128 bits in total). Also, many of the special function registers (SFR's) are bit addressable as well (in particular, those with byte addresses ending in 0 or 8 for the 8051 architecture).To support this, the 8051 has a number of instructions that operate directly on bits, such as set/clear/complement bit, jump if bit is set/not set, etc. These are much more efficient that loading up a general-purpose register and using AND or OR instructions.For example, the instruction to set bit 3 of byte address 0x2A would be (the value 53h is found in the above table):SETB 53hwhich is a 2-byte, 1 cycle instruction.Likewise, most C compilers for the 8051 (for example Keil C51) support a bit type in addition to standard C types like char, short, int etc. C statements referencing bit variables are compiled into code using the bit-manipulation assembly instructions.So the code:bit flag; . . .flag = 1;would compile into a single SETB instruction like the example above.EDIT: Regarding endianness on bit addressable machines, in general bits in a byte are labelled 7 to 0 (MSB to LSB), as in the diagram above. This is true whether the byte endianness is big endian like Motorola 6800, 68000 and PowerPC, or little endian like the 6502 family, Intel x86, and Amtel AVR.Oddly, DEC minicomputers 50 years ago used the reverse notation: the PDP-8 numbered bits 0 to 11 (MSB to LSB). These machines were not bit-addressable however. DEC changed to the more common form used today when they came out with the PDP-11. |
_codereview.86650 | Someone asked me We know that \$12^2 = 144\$ and that \$38^2 = 1444\$. Are there any other perfect squares in the form?Here is my code:public class OneFours {public static void main(String args[]) { final int power_of_ten = 8; int num = 14; for (int i = 0; i <= Math.pow(10, power_of_ten); i++) { if (Math.pow((int) Math.sqrt(num), 2) == num) { System.out.println(num + is a perfect square with root + Math.sqrt(num)); } if (i % (Math.pow(10, power_of_ten) / 100) == 0) System.out.println(--- Progress + (int)((i / Math.pow(10, power_of_ten)) * 100) + % complete); num = num * 10 + 4; }}} | Finding whether a number of the form 1444....4 is a perfect square | java;mathematics | I suggest you modularize your code writing a function to check for perfect squares:public static boolean isPerfectSquare(int n) { return Math.pow((int) Math.sqrt(n), 2) == n;}And you then you can call it:if (isPerfectSquare(num)) { System.out.println(num + is a perfect square with root + Math.sqrt(num)); }You should also take care of always putting braces, namely if (i % (Math.pow(10, power_of_ten) / 100) == 0) System.out.println(--- Progress + (int)((i / Math.pow(10, power_of_ten)) * 100) + % complete);should become if (i % (Math.pow(10, power_of_ten) / 100) == 0) { System.out.println(--- Progress + (int)((i / Math.pow(10, power_of_ten)) * 100) + % complete); }typing braces takes a fraction of a second, fixing bugs caused by not writing them may take hours.And make sure you get your indentation correct, after some tweaking in my ide I your code looks like this:public class OneFours { public static boolean isPerfectSquare( int n) { return Math.pow((int) Math.sqrt(n), 2) == n; } public static void main(String args[]) { final int power_of_ten = 8; int num = 14; for (int i = 0; i <= Math.pow(10, power_of_ten); i++) { if (isPerfectSquare(num)) { System.out.println(num + is a perfect square with root + Math.sqrt(num)); } if (i % (Math.pow(10, power_of_ten) / 100) == 0) { System.out.println(--- Progress + (int)((i / Math.pow(10, power_of_ten)) * 100) + % complete); } num = num * 10 + 4; } }} |
_cstheory.5810 | Here's my precise situation: I have a graph with nodes $V$ and edges $E$, and the nodes have some non-negative integer weights $w_i$. In one step of the protocol, I am now allowed to move weight around among nodes. This is expressed through a flow $f$ defined on the edges: $f(i,j)$ tells me how much weight I transfer from $i$ to $j$.The flow cannot create new weight. The flow must be integer.$f(i,j)$ is allowed to be larger than $w_i$, but after the entire flow has been applied all the $w_i$ must be non-negative again.Let $\Delta_i$ be the total change in the weight on node $i$, with the sign convention such that $\Delta_i$ is positive if more tasks leave node $i$ than arrive at $i$. An upper bound on $\Delta_i$ is $w_i$, by virtue of the third condition on the flow. My question now is: Is there also a lower bound? A naive lower bound for each $\Delta_i$ would be given by the sum of the $\Delta_j$ for all neighbors of $i$, but I wonder if some network- and graph-theory can find better bounds?If a good lower bound on the $\Delta_i$ is not possible, maybe there is a good \emph{upper} bound on the quantity $$\sum_{i \in V} \Delta_i^2$$? | Given a network flow, are there bounds on the change in weight on nodes? | ds.algorithms;graph theory;application of theory;network modeling | I think you're using a confusing sign convention, but I'll stick with it. It's pretty easy to see that for any connected graph you can have all weight flowing into a single vertex (unless I'm misunderstanding something), so the lower bound you'll get is $$\Delta_i\geq -\sum_{i\in V}w_i.$$Things won't really be better for bounding the square. For example, if your graph is a star in which every leaf has $w_i=1$, then $$\sum_{i\in V}\Delta_i^2 = (|V|-1)+(|V|-1)^2.$$You can't get a neighbourhood restriction, either, because you can take the example of a $k$-ary tree in which every leaf has weight 1 and all the weight goes to the root.What you can get, however, is the possibly useful bound $$\sum_{i\in V}{|\Delta_i|} \leq 2\sum_{i\in V}w_i.$$To see this, just note that when charge leaves a vertex you'll count it twice. |
_webapps.99142 | I'm working on a spreadsheet that records logistics reports via a Google form. We have 100 locations and logistics personal visit and report on condition of each location, i.e. the location needs maintenance etc.We have 3 categories of location: Priority locations that need to be visited daily, secondary locations that need to be visited a minimum every other day, and other locations that we aim to visit a minimum of every 3 days.Each logistics visit is recorded in the spreadsheet via the form it captures:Column A = Time Stamp, Column B = Location, Column C = Damage Yes/No, Column D = Damage Description, Column E = Personnel ID, I want to create a query that groups the entries by location so that only the last visit for each location is displayed. And use conditional formatting relating to latest visit date to highlight:Green visited today,Amber visited yesterday,Red visited three days ago. | Query using group by but only displaying the latest entry for each item | google spreadsheets;google spreadsheets query | Query is not an option for your task, try this formula:=ArrayFormula(VLOOKUP(UNIQUE(FILTER(B2:B,B2:B<>)),QUERY(SORT(A2:E,1,false),select Col2, Col1, Col3, Col4, Col5),{2,1,3,4,5},0)) |
_webapps.101263 | In YouTube, we can click on History and see the videos we've been playing from the most recent to the earlier plays.I spent the night listening to a friend selecting music from YouTube and I want to get a list of the links he played so I can listen to them again at home. | How can I export YouTube's personal history? | youtube | null |
_codereview.108144 | In this project I'm working on, I need to extract articles text from their original HTML document. This class, HtmlConnection, receives the URL of the article, and eventually it needs to produce a collection of the paragraphs inside the article. I'm using HTML agility pack and XPath to extract only relevent text from the article, removing irrelevant text that comes alongside in the HTML, such as JavaScript, etc. Notice that this class does not produce the final text of the article (another class deals with it), but rather a HtmlNodeCollection that consist of all the paragraphs in the article.There is one main issue in the code: It's too slow.I did some test, and came up with these numbers:Number of articles downloaded: 25Average download time: 4958 MilisecondsThis is too much. As you can see, just 25 articles take about 2 minutes. And I plan to download hundreds of articles per run. It could be a problem with my internet connection, but when I'm surfing normally, it's pretty fast and clean.Imports HtmlAgilityPackImports System.Text.RegularExpressionsImports System.Net''' <summary>''' Represents a single Html document.''' </summary>Public Class HtmlConnection ' XPath for all the paragraphs inside the body. Private Const BodyPath As String = //body//p ' RegEx for a single word. Private Const WordPath As String = [a-zA-Z]+ ''' <summary> ''' Constructor to initialize Url property ''' and to call the DownloadHtml sub. ''' </summary> ''' <param name=url> ''' The Url of the current article. ''' </param> Public Sub New(ByVal url As String) Me.Url = url DownloadHtml() End Sub ' Constructor ''' <summary> ''' Represents the Url of the current article. ''' </summary> Private Property Url As String ''' <summary> ''' Represents all the Html code ''' received from the article. ''' </summary> Private Property FullHtml As HtmlDocument Private _BodyHtml As HtmlNodeCollection ''' <summary> ''' Represents the Html of all the paragraph inside the body. ''' </summary> Public Property BodyHtml As HtmlNodeCollection Get Return _BodyHtml End Get Set(value As HtmlNodeCollection) Dim WordsMatches As MatchCollection _BodyHtml = value ' Iterate through all the paragraphs in order to ' count the number of words in them. We assume that a ' paragraph should be more then 10 words at least in order ' to be considered as part of the article, and not as an ' irrelevant text, such as the name of the author or a date, ' which are usually presented in an independent paragraph. ' We operate in a descending order to prevent wrong ' filtration or an index was out of range error. For Paragraph As Integer = value.Count - 1 To 0 Step -1 WordsMatches = Regex.Matches(value.Item(Paragraph).InnerText, WordPath) If WordsMatches.Count < 10 Then _BodyHtml.RemoveAt(Paragraph) End If Next End Set End Property ''' <summary> ''' Creates a new Html DOM using XPath. ''' </summary> Private Sub DownloadHtml() ' HtmlWeb uses Http protocol to download ' Html documents according to a certain Url. Dim HtmlWeb As HtmlWeb = New HtmlWeb FullHtml = New HtmlDocument ' Because BodyHtml is a collection, it needs to be ' initialize. Thus, we create a new HtmlNodeColleciton ' that does not actually possess any nodes, but now ' we can add to it new elements without causing an ' object reference not set to an instance of an object error. _BodyHtml = New HtmlNodeCollection(FullHtml.DocumentNode) FullHtml = (HtmlWeb.Load(Url)) ' Fix any nodes error that may ' occur inside the html code. FullHtml.OptionFixNestedTags = True BodyHtml = FullHtml.DocumentNode.SelectNodes(BodyPath) End SubEnd Class | Downloading HTML documents from the web | performance;vb.net;url | Let's break down your code and look at what you're doing wrong/right and what can be improved.I - ClassPublic Class HtmlConnectionThe name of your class is quite misleading as it's not a connection object as per se. It's an object which contains html. The underlying HttpClient used in HAP is closer to being (if not is) a html connector. So we'll rename the class so that it reflects what it is/represents, a html article.Public Class HtmlArticleII - ConstantsPrivate Const BodyPath As String = //body//pPrivate Const WordPath As String = [a-zA-Z]+This is good! You're using constants instead of magic strings/numbers. Nothing to change here except that I'll introduce a new constant.Private Const MinLength As Integer = 10III - FieldsPrivate _BodyHtml As HtmlNodeCollectionFields should be placed at the top and written in lowerCamelCase. It's also a bad habit to start a member name with an underscore as this makes your code non CLS compliant if the member is anything other than private.We'll rename the member and introduce a new one. I'll explain why later.Private m_url As StringPrivate m_paragraphs As HtmlNodeCollectionIV - ConstructorsPublic Sub New(ByVal url As String) Me.Url = url DownloadHtml()End SubYou're doing a very big mistake in the constructor. It's doing too much work. Constructors should be as light as possible. The html should only be downloaded when needed, when you decide to invoke DownloadHtml. Same logic applies for the SqlConnection class. It doesn't invoke Openin the constructor. You have to do this as a separate call.Your casing is correct but you can remove the ByVal keyword as this is default by design. I'll introduce a new parameter and make the constructor private. More about that later.Private Sub New(url As String, paragraphs As HtmlNodeCollection) Me.m_url = url Me.m_paragraphs = paragraphsEnd SubV - PropertiesPrivate Property Url As StringPrivate Property FullHtml As HtmlDocumentPublic Property BodyHtml As HtmlNodeCollection Get Return _BodyHtml End Get Set(value As HtmlNodeCollection) Dim WordsMatches As MatchCollection _BodyHtml = value For Paragraph As Integer = value.Count - 1 To 0 Step -1 WordsMatches = Regex.Matches(value.Item(Paragraph).InnerText, WordPath) If WordsMatches.Count < 10 Then _BodyHtml.RemoveAt(Paragraph) End If Next End SetEnd PropertyPrivate auto-implemented get-set properties should always be turned into fields. You should avoid heavy code in properties. Properties should mainly be used to get and set the value of a backing field, not processing data. The code should be moved to the DownloadHtml method.The expression WordsMatches.Count < 10 contains a magic number (10) which should be turned into a constant (ref. the beginning of the review).I don't see any real use of the FullHtml property other than storing a reference so we'll change the scope and remove it.The name of the BodyHtml property is misleading. It's not a html body. It contains our paragraphs so we'll name it accordingly. Same reason why we changed the name of the backing field earlier.The name of the Url property is good so we'll keep that.Since the backing fields of the properties are provided in the constructor we'll remove the setters and mark the properties read only.Public ReadOnly Property Paragraphs As HtmlNodeCollection Get Return Me.m_paragraphs End GetEnd PropertyPublic ReadOnly Property Url As String Get Return Me.m_url End GetEnd PropertyVI - MethodsPrivate Sub DownloadHtml() Dim HtmlWeb As HtmlWeb = New HtmlWeb FullHtml = New HtmlDocument _BodyHtml = New HtmlNodeCollection(FullHtml.DocumentNode) FullHtml = (HtmlWeb.Load(Url)) FullHtml.OptionFixNestedTags = True BodyHtml = FullHtml.DocumentNode.SelectNodes(BodyPath)End SubThis method should be public and it should do all the heavy work. I also suggest you make it static (shared) and return an instance of our class based on downloaded data. Doing this makes it obvious why we made the constructor private and the properties read only.Public Shared Function Download(url As String) As HtmlArticle If (String.IsNullOrWhiteSpace(url)) Then Throw New ArgumentNullException(NameOf(url)) End If Dim web As New HtmlWeb() Dim document As HtmlDocument = web.Load(url) document.OptionFixNestedTags = True Dim paragraphs As HtmlNodeCollection = document.DocumentNode.SelectNodes(HtmlArticle.BodyPath) For index As Integer = (paragraphs.Count - 1) To 0 Step -1 If (Regex.Matches(paragraphs.Item(index).InnerText, HtmlArticle.WordPath).Count < HtmlArticle.MinLength) Then paragraphs.RemoveAt(index) End If Next Return New HtmlArticle(url, paragraphs)End FunctionVII - ImprovmentsSo, how can we improve the performance of our class?One possible solution is to add an overload which accepts multiple urls and run the download in parallel. The more cores your computer got, the better the result.You might think that this requires a lot of coding but this is not the case. All you need is a thread safe list and the TPL extension method will do the rest.Public Shared Function Download(urls As IEnumerable(Of String)) As List(Of HtmlArticle) If (urls Is Nothing) Then Throw New ArgumentNullException(NameOf(urls)) End If Dim bag As New ConcurrentBag(Of HtmlArticle) urls.AsParallel().ForAll(Sub(url) bag.Add(HtmlArticle.Download(url))) Return bag.ToList()End FunctionResultPublic Class HtmlArticle Private Const BodyPath As String = //body//p Private Const WordPath As String = [a-zA-Z]+ Private Const MinLength As Integer = 10 Private m_url As String Private m_paragraphs As HtmlNodeCollection Private Sub New(url As String, paragraphs As HtmlNodeCollection) Me.m_url = url Me.m_paragraphs = paragraphs End Sub Public ReadOnly Property Paragraphs As HtmlNodeCollection Get Return Me.m_paragraphs End Get End Property Public ReadOnly Property Url As String Get Return Me.m_url End Get End Property Public Shared Function Download(url As String) As HtmlArticle If (String.IsNullOrWhiteSpace(url)) Then Throw New ArgumentNullException(NameOf(url)) End If Dim web As New HtmlWeb() Dim document As HtmlDocument = web.Load(url) document.OptionFixNestedTags = True Dim paragraphs As HtmlNodeCollection = document.DocumentNode.SelectNodes(HtmlArticle.BodyPath) For index As Integer = (paragraphs.Count - 1) To 0 Step -1 If (Regex.Matches(paragraphs.Item(index).InnerText, HtmlArticle.WordPath).Count < HtmlArticle.MinLength) Then paragraphs.RemoveAt(index) End If Next Return New HtmlArticle(url, paragraphs) End Function Public Shared Function Download(urls As IEnumerable(Of String)) As List(Of HtmlArticle) If (urls Is Nothing) Then Throw New ArgumentNullException(NameOf(urls)) End If Dim bag As New ConcurrentBag(Of HtmlArticle) urls.AsParallel().ForAll(Sub(url) bag.Add(HtmlArticle.Download(url))) Return bag.ToList() End FunctionEnd ClassUsageDim url As String = urlDim singleArticle As HtmlArticle = HtmlArticle.Download(url)Dim urls As New List(Of String)urls.Add(url 1)urls.Add(url 2)urls.Add(url 3)'etc...Dim multipleArticles As List(Of HtmlArticle) = HtmlArticle.Download(urls) |
_unix.288435 | I have a machine hosting an LDAP database and services on other machines run as users from that database. Because the user accounts does not exist locally, the services fail to start when those machines boot before the machine hosting the LDAP database.All the machines are running Ubuntu 14.04 except for one that is running CentOS 7. Is it possible with upstart and systemd to wait for the LDAP database to be available before starting certain services?EDIT:I've tried using a pre-start script with Upstart that loops until LDAP is available, but that doesn't work. I found in the Upstart cookbook that the pre-start script is run as user and group specified with setuid and setgid. So the pre-start script is never run because the user and group doesn't exist until the LDAP service is running on another machine.I tried specifying respawn as well but that didn't help in this case. From what I understand from the Upstart cookbook, respawn only takes effect when the main script or executable fails. Thus, the service is not restarted because the service fails before any script is run. | How to start a service on boot after ldap account is available | services;ldap;upstart | null |
_unix.263763 | My system generates a flat file with 7 arguments :Field1,Field2,Field3,Field4,Field5,Field6,Field7Field1,Field2,Field3,Field4,Field5,Field6,Field7Field1,Field2,Field3,Field4,Field5,Field6,Field7Field1,Field2,Field3,Field4,Field5,Field6,Field7Field1,Field2,Field3,Field4,Field5,Field6,Field7Each of these fields is an argument to a script.I wish to run the script iteratively (for each line of my file).This is what I am doing, but it skips the first line of my file.e.g.name of my file = v_jaylocation = /vjay/projectlocation of script = /script/vjayscript.kshcat /vjay/project/v_jay | while read in; do while IFS=, read aa bb cc dd ee ff gg ; do /script/vjayscript.ksh $aa $bb $cc $dd $ee $$ff $gg; donedone | Parsing a delimited in ksh as command argument | shell script;scripting;ksh;csv;arguments | Try this (i.e. get rid of the seemingly pointless while read in):cat /vjay/project/v_jay | while IFS=, read aa bb cc dd ee ff gg ; do /script/vjayscript.ksh $aa $bb $cc $dd $ee $ff $gg done |
_unix.387548 | /etc/init.d/umountfs is run during shutdown to unmount most filesystems. It contains this:PROTECTED_MOUNTS=$(sed -n ':a;/^[^ ]* \(\/\|\/usr\) /!{H;n;ba};{H;s/.*//;x;s/\n//;p}' /proc/mounts)This command apparently selects a subset of the lines in /proc/mounts, which then become exempt from being unmounted later in the script.It matches lines with / or /usr in the second field (the mount point) and then what it does next involves too many exotic sed features for me to figure out what the intent is.It would make sense if this was just selecting the / and /usr lines, since those get unmounted in a different script. But it doesn't do that. When I run it on my actual /proc/mounts, $PROTECTED_MOUNTS ends up containing almost all the lines, including the /home line. It's not good if /home doesn't get unmounted, so that can't be right.What could the writer of that sed command possibly have meant to do, with all that branching and hold space stuff? | What is the sed command in Debian's /etc/init.d/umountfs supposed to do? | sed | I'll give it a shot...This will return every line up to and including the last occurrence of / or /usr. AKA this strips everything after the last occurrence of either of those. :a;/^[^ ]* \(\/\|\/usr\) /!{H;n;ba};This says, for lines that don't contain exactly / or /usr in the second (whitespace delimited) column, append to Hold space, fetch next line, loop back to label a.{H;s/.*//;x;s/\n//;p}We'll only get here if we encounter a line with / or /usr. Then we append to Hold space (which has everything from the first section), clear pattern space, exchange hold space with pattern space, remove first newline from pattern space and print it.After we've seen the last / or /usr line (and we've printed everything up to that point), we loop through the first part and suck all the remaining non-matching lines up...but they never get printed since we don't enter the second part.I did a bit of testing and that has been consistent with my claim.Clearly this depends on some kind of ordering being maintained in /proc/mounts. But the list is simply built according to the order that the mount points are created. So wherever that is done must be maintained or this stuff will break, I guess. It all seems awfully brittle to me. |
_cstheory.3684 | I have a sparse weighted graph, and I want to find the longest path from a given vertex to any other vertex which does not go through the same vertex twice. You can think of it as, I am here, and I want to take the longest walk possible in my graph without walking through the same place twice. Where ever that ends me up, I don't care, and I don't necessarily have to travel through every point on the graph, if those points do not lie on the longest path. All edges have positive weights.Can anyone describe an algorithm for this that is not a complete enumeration of all paths? | Max Non-overlapping Path in Weighted Graph | ds.algorithms;graph algorithms | Yes, the Bellman-Held-Karp algorithm is not a complete enumeration and can be modified easily enough to solve your problem.However, it still takes something over $2^n$ time (see question for details), and something exponential like that seems unavoidable since this is a variant of the traveling salesman problem. |
_codereview.972 | I'm quite new to JavaScript, and I'd like a review of the code structure and syntax. It serves this little online regexp test (still a work in progress).The whole code (JavaScript, CSS & HTML) is on GitHub.application.js:function update_result_for(input, regexp_value) { var input_value = input.val(); var result_spans = input.parent().children('span'); if(!input_value || !$('#regexp').val()) { result_spans.hide(); } else { var regexp = new RegExp(regexp_value); var result = regexp.exec(input_value); if(result) { var matched_string = result.shift(); var submatches_list_string = jQuery.map(result, function(submatch, index) { return '$' + (index + 1) + ' = ' + submatch; }).join('; '); var regexp_to_highlight_matched_string = new RegExp('(.*)' + matched_string + '(.*)'); var regexp_to_highlight_matched_string_result = regexp_to_highlight_matched_string.exec(input_value); var before_matched_string = regexp_to_highlight_matched_string_result[1]; var after_matched_string = regexp_to_highlight_matched_string_result[2]; var input_value_with_matched_string_highlighted = 'matched: ' + before_matched_string + '<span class=matched>' + matched_string + '</span>' + after_matched_string; result_spans.filter(.submatches).text(submatches_list_string); result_spans.filter(.match).html(input_value_with_matched_string_highlighted); result_spans.filter(.ok).show('fast'); result_spans.filter(.not_ok).hide(); } else { result_spans.filter(.not_ok).show('fast'); result_spans.filter(.ok).hide(); } }} // from http://www.scottklarr.com/topic/126/how-to-create-ctrl-key-shortcuts-in-javascript/var isCtrl = false;$(document).keyup(function (e) { if(e.which === 17) isCtrl=false;}).keydown(function (e) { if(e.which === 17) isCtrl=true; if(e.which === 69 && isCtrl) { $('#regexp').focus(); return false; }});$(document).ready(function() { $('#regexp').focus(); $('span.result').hide(); $('input:not(#regexp)').live(keyup, function() { update_result_for($(this), $('#regexp').val()); }); $('input#regexp').keyup(function() { $('input:not(#regexp)').each(function(i) { update_result_for($(this), $('#regexp').val()); }); }); $('a.add_example').click(function() { new_example = $('div#examples p:last').clone(); new_example.children('input').attr('value', ''); new_example.children('span').hide(); new_example.insertBefore($(this)); new_example.children(input).focus(); });}); | JavaScript portion of regexp tester | javascript;jquery | This code looks fine to me for a toy project. I especially appreciate the long names for identifiers.Now, it could look better:with more comments. You should describe the intent (the why behind the how) and the expected use case for the function: type and range of values in parameters, one line to describe what it does, and one more paragraph for details if needed.my personal preference would be to use camelCase instead of underscore_between_words for long names. Although this is open to discussion.a little trick: end the if branch with return; to avoid nesting all remaining code in the else branch:function update_result_for(input, regexp_value) { var input_value = input.val(); var result_spans = input.parent().children('span'); if(!input_value || !$('#regexp').val()) { result_spans.hide(); return; // return as soon as possible to avoid deep nesting } // no need for else var regexp = new RegExp(regexp_value); var result = regexp.exec(input_value); // ...}in the same vein, treat exceptional cases first and normal cases after. This is a useful convention which helps the reader, and the exception handling is usually shorter (or should be extracted to a separate function if longer) which avoids long runs of nested code:if (!result) { result_spans.filter(.not_ok).show('fast'); result_spans.filter(.ok).hide(); return;}// reduced nestingvar matched_string = result.shift();// ...only use anonymous functions when you actually need a closure with access to the context: the intent of the function will be clearer with a name, you will avoid nesting, and may reuse the function more easily including for unit testing. There are many anonymous functions in your code, which makes it harder to understand:function(submatch, index) { return '$' + (index + 1) + ' = ' + submatch;})function(e) { if(e.which === 17) isCtrl=false;}function(e) { if(e.which === 17) isCtrl=true; if(e.which === 69 && isCtrl) { $('#regexp').focus(); return false; }})function() { $('#regexp').focus(); $('span.result').hide(); // ...}function() { update_result_for($(this), $('#regexp').val());}function() { $('input:not(#regexp)').each(function(i) { update_result_for($(this), $('#regexp').val()); }); }function() { new_example = $('div#examples p:last').clone(); new_example.children('input').attr('value', ''); new_example.children('span').hide(); new_example.insertBefore($(this)); new_example.children(input).focus();}once you define more than one function, you should wrap your code in a closure to avoid cluttering the global namespace, following the Module Pattern:(function(){ // private scope for your code}());break long lines to fit in about 80 characters to avoid the need for scrolling horizontally in typical console windows and in code areas on this site:var regexp_to_highlight_matched_string = new RegExp('(.*)' + matched_string + '(.*)');var regexp_to_highlight_matched_string_result = regexp_to_highlight_matched_string.exec(input_value);var before_matched_string = regexp_to_highlight_matched_string_result[1];var after_matched_string = regexp_to_highlight_matched_string_result[2];var input_value_with_matched_string_highlighted = 'matched: ' + before_matched_string + '<span class=matched>' + matched_string + '</span>' + after_matched_string;To go further, my advice would be to read JavaScript: The Good Parts and start using JSLint, in this order: this is an enlightening experience on your way to mastering JavaScript. The other way round, using the tool without understanding the mindset of its author, is very frustrating.I ran JSLint on your code. It has one critical complaint hidden among hair splittings: the declaration of new_example is missing, it is therefore a global variable which is susceptible to result in unexpected bugs. // var keyword added: var new_example = $('div#examples p:last').clone(); |
_codereview.47706 | Is this an efficient way to handle page requests in MVC?index.php:require 'Classes/Autoloader.php';Autoloader::start();Session::start();new Bootstrap();Bootstrap.phpclass Bootstrap { private $controller = null, $action = null, $args = null; public function __construct() { $this->manage_url(); if($this->page_exist()){ $this->request(); } else { $error = new ErrorController(); $error->error404(); } } private function request(){ $controller = new $this->controller(); if(!$this->args){ $controller->{$this->action}(); } else{ $count_args = count($this->args); switch ($count_args) { case 1: $controller->{$this->action}($this->args[0]); break; case 2: $controller->{$this->action}($this->args[0], $this->args[1]); break; case 3: $controller->{$this->action}($this->args[0], $this->args[1], $this->args[2]); break; case 4: $controller->{$this->action}($this->args[0], $this->args[1], $this->args[2], $this->args[3]); break; } } } /** * Get controller, action and parametes */ private function manage_url(){ $uri = $_SERVER['REQUEST_URI']; $uri = trim($uri, '/'); $this->remove_query_or_hash($uri); $exploded_uri = explode('/', $uri); $this->controller = Util::istruthy_or($exploded_uri[0], 'Main').'Controller'; $this->action = Util::istruthy_or($exploded_uri[1], 'index'); $this->args = array_slice($exploded_uri, 2); } private function remove_query_or_hash(&$uri){ $query = strpos($uri, '?'); $hash = strpos($uri, '#'); if($query!==FALSE||$hash!==FALSE){ $idx = $query < $hash ? $hash : $query; $uri = substr($uri, 0, $idx); } } private function page_exist(){ $controller = class_exists($this->controller); $method = method_exists($this->controller, $this->action); if(!$controller||!$method){ return FALSE; } return TRUE; }}Util istruthy_or():public static function istruthy_or(&$var, $val = NULL){ return isset($val) ? ($var ? $var : $val) : ($var ? $var : NULL);} | Handling page requests in MVC | php;mvc | Your approach is great as long as you are the only one working with this code and all your uri ideally resolve to /controller/action/args. Problems will start when your client asks for a friendly uri like /my-section/my-page or someone else will have to maintain your code.To address the problem with uri you might need custom routing (rules for non-standard uri routing that apply before the standard /controller/action/args). For examples of such rules you should check how it's done in different frameworks and find the one that fits your liking. Here's how it's done in CodeIgniter.Second issue is a bit less clear. By looking at your code:Autoloader::start();Session::start();new Bootstrap();One will never realise where exactly is the job gets done. You could do it a lot clearer by chaning, for example, to this:$bootstrap = new Bootstrap();$bootstrap->process_request($_SERVER['REQUEST_URI']);But that's not the only issue. Next you call manage_url(), which does not get any paramteter and therefore is untestable. You could make it testable by calling it with a parameter manage_url($uri) - this way you can call it in a test with different uris and see how it handles it's job. Then again, what is it's job? It does multiple things, thats why such a non-telling name.You could make your code a lot more clear for future developers (including yourself) by making each function do one task. For example:public function process_request($uri){ // first you want a function to clear uri from unwanted parts $uri = $this->prepare_uri($uri); // then you want to apply custom routing I described earlier if (!$this->apply_custom_routing($uri)) { // if none matched, apply default routing of your manage_url()'s last part if (!$this->apply_default_routing($uri)) { // none valid routing found - 404 $this->apply_error_routing(); } } // now you know request details and can proceed $this->call_controller();}Note that it's now pretty clear what each function does and each of them is at least somewhat testable, because their dependencies are clear.Also note, that you don't need that ugly switch statement in request(). There is a function for that type of situations (when you don't know amount of arguments beforehand):call_user_func_array(array($this->controller, $this->action), $this->args); |
_unix.361507 | I'm trying to implement vlans on a target programmatically. But first I wanted to set up vlans manually to help get a better understanding of vlan setup. So I setup a vlan manually on my development system (ubuntu) using the vconfig/ifconfig command combination, but using the same command combination on the intended target doesn't work.Both systems use the same 8021q driver so the method of informing the lower level Ethernet driver of the vlan info should be the same (I would think). After looking at the vlan driver source it appears that it collects the vlan info and adds the info the sk_buff structure which is eventually passed to the ethernet driver, but it's not obvious where the vlan magic is suppose to happen (ethernet driver or 8021q driver).I looked at the source for the target systems ethernet driver and it supports an ioctl method of setting up a vlan. But this does not seem like the conventional way that Linux sets up a vlan in the ethernet driver. By what mechanism does the vlan driver (8021q.ko) tell the Ethernet hardware about a vlan? Is it a special api call to the ethernet driver to set up a vlan in hardware, or should the vlan driver be adding the vlan tags to the packet?Any info on vlan implementation would also be helpful too. | How does vlan driver pass vlan info to the h/w ethernet driver | linux;vlan;system programming | null |
_unix.379789 | How can I start a service unit only if another service unit runs without any errors?I have 2 service units:#echo-date-0.service[Unit]Description=[Service]ExecStart=/home/user/bash/echo-date-0.sh[Install]WantedBy=multi-user.target#echo-date-1.service[Unit]Description=[Service]ExecStart=/home/user/bash/echo-date-1.shRequires=echo-date-0.serviceAfter=echo-date-0.service[Install]WantedBy=multi-user.targetI have the script echo-date-0.sh returning exit code 1 (exit 1), and if I check the status of echo-date-0.service I see: Active: failed (Result:exit-code) Process: (code=exited, status=1/FAILURE)But, echo-date-1.service runs even though I have it Requiring echo-date-0.service. How can I stop echo-date-1.service from running, if echo-date-0.service fails? | systemd start a service only if another service runs without errors | systemd | null |
_webmaster.11784 | A don't understand why the sidebar of my Wordpress blog does not have consistent formatting for H3 tags. There are two PHP-generated un-styled H3 tags in the sidebar, followed by my own manual H3 tag. The first two appear larger than the third, yet they are identical tags.The site in question is here.The contents of sidebar.php are:<div class=sidebar><?php if ( !function_exists('dynamic_sidebar') || !dynamic_sidebar('Sidebar') ) : $widget_args = array( 'after_widget' => '</div></div>', 'before_title' => '<h3>', 'after_title' => '</h3><div class=widget-body clear>' );?><?php the_widget( 'GetConnected', 'title=Get Connected', $widget_args); ?><?php the_widget( 'Recentposts_thumbnail', 'title=Recent posts', $widget_args); ?><?php endif; ?></div><div class=sidebar><h3>Choice links</h3><p> </p><ul> <li><a href=http://www.annimac.com.au>Annimac Consultants</a> - Futurist & Life Coach</li> <li><a href=http://www.melvilletenniscentre.com.au>Melville Tennis Centre</a> - Great social tennis</li></ul> </div> | Wordpress CSS formating issue | css;wordpress | You have a wrong selector in your CSS stylesheet. It is .widget h3, but should be .sidebar h3 (look into your HTML code). Besides - <p> </p> is a big no, no. One does not set the layout using empty and not semantically neutral block elements. Just use margins or paddings instead. |
_unix.5723 | I am looking for a book about the Unix command-line toolkit (sh, grep, sed, awk, cut, etc.) that I read some time ago. It was an excellent book, but I totally forgot its name. The great thing about this specific book was the running example. It showed how to implement a university bookkeeping system using only text-processing tools. You would find a student by name with grep, update grades with sed, calculate average grades with awk, attach grades to IDs with cut, and so on. If my memory serve, this book had a black cover, and was published circa 1980.Does anyone remember this book? I would appreciate any help in finding it. | Looking for an old classical Unix toolkit textbook | text processing;books | null |
_codereview.37728 | I made a simple Universal-File-Duplicator (Example: make 125 duplicates of one file).Very useful if you want to fill a whole USB flash drive or an old harddisk with an important file (Example: Bitcoin wallet.dat or privatekey) and you don't want to hit Ctrl+V all the time...Suggestions? Improvements?#include stdafx.h#include stdio.h#include <stdlib.h>#include <strstream>#include <string>#include <iostream>#include <fstream>#include <conio.h>using namespace std;int main(int argc, char* argv[]){ char nummer[1000000], sourcefile[255], targetfile[255], targetfileneu[255], endung[255]; int i = 0; int anzahl = 0; ifstream Quelldatei; printf(Welcome! You are using UNIVERSAL-DATEI-DUPLIKATOR v1.0\n); printf(Filename? (Example: test.txt)\n); gets(sourcefile); printf(New Filename without ending? (Example: filename)\n); gets(targetfile); printf(Ending? (Example: .txt)\n); gets(endung); printf(How many times do you want to create the file?\n); scanf(%d, &anzahl); for (i = 0; i < anzahl; i++) { sprintf(nummer, %ld, i); strcpy(targetfileneu, targetfile); strcat(targetfileneu, nummer); strcat(targetfileneu, endung); printf(Targetfilename: %s\n, targetfileneu); Quelldatei.open(sourcefile, ios::binary); if (!Quelldatei) { cerr << ERROR!\n; return 0; } ofstream Zieldatei(targetfileneu, ios::binary); if (!Zieldatei) { cerr << ERROR!\n; return 0; } else { int c; while ((c = Quelldatei.get()) >= 0) { Zieldatei.put(c); } } memset(&targetfileneu[0], 0, sizeof(targetfileneu)); Quelldatei.close(); Zieldatei.close(); } printf(SUCCESS!\n); system(pause); return 0;} | Universal File Duplicator | c++;file;console | null |
_softwareengineering.337705 | Studying beginners course on hardware/software interface and operating systems, often come up the topic of if it would be better to replace some hardware parts with software and vice-versa. I can't make the connection. | What is meant by the phrase Software can replace hardware? | interfaces;operating systems;software;hardware | null |
_cstheory.3349 | There are well known techniques for proving lower bounds on the communication complexity of boolean functions, like fooling sets, the rank of the communication matrix, and discepancy. 1) How do we use these techniques for lower bounding partial boolean functions? More specifically, how do you count the rectangles in the communication matrix? Do you also count the undefined part of the function? Or do you leave it out?Another thing, what are the known relations between the communication complexity of total and partial functions? For example, is there a function $f$ with a promise version of it, call it $f'$, such that $C(f)\neq C(f')$? (here $C$ could be any communication complexity measure like deterministic, probabilistic with all its flavors, quantum). A concrete example is the equality function EQ, and its promise version defined in this paper denoted as EQ'. It is known that $C(EQ)=n$ and $C(EQ')=\Omega(n)$ where $C$ is the bounded error communication complexity (see the paper). There is no matching upper bound here, but they are asymptotically the same.2) Is there a function defined in the same spirit of EQ and EQ', but with a different complexity? | Communication lower bounds for partial boolean functions | cc.complexity theory;lower bounds;communication complexity;boolean functions | (1) The way I like to think about partial functions is by defining a total function with three outputs e.g, $f: \{0,1\}^n \times \{0,1\}^n \rightarrow \{0,1, *\}$. The $*$ values are where your partial function is undefined. (2) You can still define a monochromatic rectangle in this case. But here, you allow $*$'s to be in the rectangle.A rectangle $R$ is monochromatic if $f(R) \subseteq \{0,*\}$ or $f(R) \subseteq \{1,*\}$. From this, you can still use many of the standard lower bounds techniques such as fooling sets.(3) As Marc mentions, you can always define trivial partial functions where the communication complexity is much less than the original. For example, say the partial function TEQ is the EQ function, restricted to $(x,y)$ pairs such that $x \neq y$. A partial function that people might care about is the Gap-Hamming-Distance function.$GHD_{n,g}$ is takes two $n$ bit strings $x,y$ and returns $1$ if their Hamming distance is more than $n/2 + g$ and returns $0$ if their Hamming distance is less than $n/2 - g$. (The Hamming distance $\Delta(x,y)$ is the number of $i$ where $x_i \neq y_i$.) People are really particularly interested in the randomized communication complexity of $GHD$. It's not hard to show that the gapless version (Alice/Bob want to tell if $\Delta(x,y)$ is greater than $n/2$ or not) requires $\Omega(n)$ bits of communication.It turns out that when $g = O(\sqrt{n})$, you still need a linear amount of communication. However, when $g = \omega(\sqrt{n})$, you can get away with only $O((n/g)^2)$ bits. When $g = \Omega(n)$, you get a partial function with $O(1)$ communication complexity.The $g = \Theta(\sqrt{n})$ case seems to be the important case. Indyk and Woodruff introduced this problem, gave a lower bound for one-way randomized protocols, and used it to get lower bounds for streaming algorithms that estimate frequency moments. The state of the art lower bound is $\Omega(n)$ bits for any randomized protocol and is due to Chakrabarti and Regev.Piotr Indyk and David Woodruff. Tight Lower Bounds for the Distinct Elements Problem. FOCS 2003.Amit Chakrabarti and Oded Regev. An Optimal Lower Bound on the Communication Complexity of Gap-Hamming-Distance. http://arxiv.org/pdf/1009.3460. |
_unix.329144 | I was reading about bash interactive and on interactive logins and found that running bash with -l option will start it as login shell but after doing so, when I ran command echo $0 to verify, it still shows as non login shell.[root@localhost ~]# bash -l[root@localhost ~]# echo $0bashIt should show - as prefix to shell name. Please confirm if I am going wrong. | Why is $0 not -bash in an interactive login shell? | bash;shell | To have an - as the first character of the command name is just one way to signal a login shell, there are other signals. In fact, the correct way to detect that the present shell is a login shell is to ask the shell itself.In the bash manual:A login shell is one whose first character of argument zero is a -, or one started with the --login option.In bash: shopt -p login_shellWill print -u if the shell is not login, and -s if it is.Lets test it:$ ln -s $(which bash) ./-bash # make a local copy of bash$ PATH=$PATH:. # Big security problem, don't use it.$ -bash # start the local copy of bash$ echo $0 # Its name start with an --bash $ shopt -p login_shell # Is it a login shell?shopt -s login_shell # Yes!, the answer is -s$ exit # leave the login shell$ PATH=${PATH%:.} # Remove the local pwd from the path.$ rm ./-bash # Remove the local copy of bashIn fact, that $0 has a - doesn't have to mean that the shell is a login shell:$ bash -c 'echo $0; shopt -p login_shell' -bash 1 2 3-bashshopt -u login_shellThe other way (from the manual) to get a login shell, is just ask for it:$ bash --login # ask for a login shell$ echo $0 # What is its name?bash$ shopt -p login_shell # Is it a login shell?shopt -s login_shell # Yes, it is!$ exit # leave the login shell. |
_cs.41491 | How can it be proved that TSP cannot be solved in polynomial time ( Please bear that I don't have a hardcore computer science background). | TSP polynomial Time | algorithms;graph theory | null |
_unix.341984 | I'm setting up MPD on rPi and using a Behringer UCA202 as output. However, I also want to use this hardware to play a line-in (eg to play video etc from my computer) - and apply an equalizer setting to both (precluding the easy answer of using the device's monitor option). So I guess:Capture hw:5,0Mix in mpd playbackSend this mix through the equaliserSend the result to hw:5,0For some reason this hardware doesn't show up in alsamixer > capture ('This sound device does not have any capture controls') but it does show up in arecord and I know I can send the input to the output, having done so from the command line with:alsaloop -C hw:5,0 -P hw:5,0I also know I can get MPD working through the equaliser:ctl.equal { type equal;}pcm.equalizer { type equal slave.pcm plughw:5,0}pcm.!default { type plug slave.pcm equalizer}I have experimented with dmix but my alsa-fu is lacking; I'm not really understanding what combination of things I need to do to get this working (if it's at all possible). Ideally avoiding installing pulse - am trying to keep this lightweight on the Pi. | ALSA mix mpd and line-in input through equaliser | audio;raspberry pi;raspbian;alsa | null |
_scicomp.8895 | Introduction:I have a vertical segment S That i want to move across a plane (Left --> Right), and find intersections with horizontal lines.Problem :The problem which i am having is the following: if the vertical segment intersects with multiple horizontal lines, as a result i'll get multiple intersections as you can you see in the following figure. Want I want is that to have just 1 intersection. Or in another way Multiple intersections, should be combined to form 1 group. The 8 intersections Should be considered as 1.As a priori information I have the START and END points of every horizontal line.I was thinking if I can Move the line by using the sweep algorithm, but i can't really figure out how to model the EVENTSThe objective is to have the following result, as shown in the following figure: | Vertical and horizontal segments intersection (Line Sweep) | algorithms;c++;computational geometry | I put this python script together from various codes I found on the web,https://stackoverflow.com/questions/563198/how-do-you-detect-where-two-line-segments-intersect?rq=1, there are plenty of good answers here, this one is from Kris.So basically,Create input list of line segmentsCreate input list of test lines (the red lines in your diagram).Iterate though the intersections of every lineCreate a set which contains all the intersection points.I have recreated you diagram and used this to test the intersection code. It gets the two intersection points in the diagram correct.C and C++ has equivalents to these data structures, and you can code the intersection algorithm in C too (it's fairly simple).from __future__ import division# Thanks to @Kris for the intersection algorithm in python# https://stackoverflow.com/questions/563198/how-do-you-detect-where-two-line-segments-intersectdef find_intersection( p0, p1, p2, p3 ) : s10_x = p1[0] - p0[0] s10_y = p1[1] - p0[1] s32_x = p3[0] - p2[0] s32_y = p3[1] - p2[1] denom = s10_x * s32_y - s32_x * s10_y if denom == 0 : return None # collinear denom_is_positive = denom > 0 s02_x = p0[0] - p2[0] s02_y = p0[1] - p2[1] s_numer = s10_x * s02_y - s10_y * s02_x if (s_numer < 0) == denom_is_positive : return None # no collision t_numer = s32_x * s02_y - s32_y * s02_x if (t_numer < 0) == denom_is_positive : return None # no collision if (s_numer > denom) == denom_is_positive or (t_numer > denom) == denom_is_positive : return None # no collision # collision detected t = t_numer / denom intersection_point = [ p0[0] + (t * s10_x), p0[1] + (t * s10_y) ] return intersection_point# Create input data.# black linesline_segments = [[(1,4), (4,4)], [(2,3), (5,3)], [(3,2), (6,2)], [(6.5, 1), (7,1)], [(7.5, 0), (8.5,0)]]# red linestest_segments = [[(4.5,0), (4.5,4.5)], [(6.25, 0), (6.25, 4.5)]]# Check all lines for intersectionsintersections = set()for test_segment in test_segments: for line_segment in line_segments: p0, p1 = test_segment[0], test_segment[1] p2, p3 = line_segment[0], line_segment[1] result = find_intersection(p0, p1, p2, p3) if result is not None: intersections.add(tuple(result))print intersections |
_cs.42617 | My algorithm book states that any n-vertex binary tree T can be partitioned by just removing a single edge into two disconnected trees A and B where neither of them has more than 3/4 of the vertices.It sounds like it should be simple to create such a tree, but I can't imagine one, my bisections are always better balanced. Can somebody show me a tree where the vertex distribution of 3/4 to 1/4?This is from Introduction to Algorithms by Thomas Cormen, 3rd edition, MIT Press. Appendix B, Problems B-3. | Worst case bisection of binary tree | binary trees | Consider a simple binary tree $T$ with only 4 nodes: The root of $T$ is $A$. $A$ has a left child $B$ which has two children $C$ and $D$. |
_webmaster.55601 | About two weeks ago I uploaded few sitemap files (few hunded thousand links total), and after a week, I saw that Google has indexed most of those links.Now, a week ago I cleaned my database a bit, which lead to about 30% of links to be invalid. I then updated my sitemap files with only valid links, and reuploaded them to Google Webmaster Tools.And here we are, a week from that, and Google still displays those invalid links.Do I need to do anything else in order to stop Google from doing that, or do I need to just wait more? | Google listing URLs that don't exist anymore | seo;google;url | null |
_scicomp.20013 | I'm Looking for an implementation of the IAPWS-IF97 water properties on C/C++.I'm aware of the library freesteam. However freesteam does not include all the properties I'm looking for. Particularly I need differential properties like dh/dp, dv/dp and in certain regions. I use a similar implementation for Octave/Matlab and I would also like to have it in C/C++. | Water Properties IAPWS-IF97 implementation on C/C++ | c | null |
_unix.364568 | As a non-root user I am running a process. The process binary has been given a cap_sys_resource capability. Even though the process is owned by the same user, that user cannot read its /proc//fd directory. The permissions in /proc/pid look like this:dr-xr-xr-x. 9 ec2-user ec2-user 0 May 12 01:03 .dr-xr-xr-x. 249 root root 0 Apr 3 13:34 ..dr-xr-xr-x. 2 ec2-user ec2-user 0 May 12 01:03 attr-rw-r--r--. 1 root root 0 May 12 01:04 autogroup-r--------. 1 root root 0 May 12 01:03 auxv-r--r--r--. 1 root root 0 May 12 01:04 cgroup--w-------. 1 root root 0 May 12 01:04 clear_refs-r--r--r--. 1 root root 0 May 12 01:03 cmdline-rw-r--r--. 1 root root 0 May 12 01:04 comm-rw-r--r--. 1 root root 0 May 12 01:04 coredump_filter-r--r--r--. 1 root root 0 May 12 01:04 cpusetlrwxrwxrwx. 1 root root 0 May 12 01:04 cwd-r--------. 1 root root 0 May 12 01:04 environlrwxrwxrwx. 1 root root 0 May 12 01:04 exedr-x------. 2 root root 0 May 12 01:03 fddr-x------. 2 root root 0 May 12 01:04 fdinfo-rw-r--r--. 1 root root 0 May 12 01:04 gid_map-r--------. 1 root root 0 May 12 01:04 io-r--r--r--. 1 root root 0 May 12 01:04 limits-rw-r--r--. 1 root root 0 May 12 01:04 loginuiddr-x------. 2 root root 0 May 12 01:04 map_files-r--r--r--. 1 root root 0 May 12 01:04 maps-rw-------. 1 root root 0 May 12 01:04 mem-r--r--r--. 1 root root 0 May 12 01:04 mountinfo-r--r--r--. 1 root root 0 May 12 01:04 mounts-r--------. 1 root root 0 May 12 01:04 mountstatsdr-xr-xr-x. 5 ec2-user ec2-user 0 May 12 01:04 netdr-x--x--x. 2 root root 0 May 12 01:03 ns-r--r--r--. 1 root root 0 May 12 01:04 numa_maps-rw-r--r--. 1 root root 0 May 12 01:04 oom_adj-r--r--r--. 1 root root 0 May 12 01:04 oom_score-rw-r--r--. 1 root root 0 May 12 01:04 oom_score_adj-r--r--r--. 1 root root 0 May 12 01:04 pagemap-r--r--r--. 1 root root 0 May 12 01:04 personality-rw-r--r--. 1 root root 0 May 12 01:04 projid_maplrwxrwxrwx. 1 root root 0 May 12 01:04 root-rw-r--r--. 1 root root 0 May 12 01:04 sched-r--r--r--. 1 root root 0 May 12 01:04 schedstat-r--r--r--. 1 root root 0 May 12 01:04 sessionid-rw-r--r--. 1 root root 0 May 12 01:04 setgroups-r--r--r--. 1 root root 0 May 12 01:04 smaps-r--r--r--. 1 root root 0 May 12 01:04 stack-r--r--r--. 1 root root 0 May 12 01:03 stat-r--r--r--. 1 root root 0 May 12 01:03 statm-r--r--r--. 1 root root 0 May 12 01:03 status-r--r--r--. 1 root root 0 May 12 01:04 syscalldr-xr-xr-x. 3 ec2-user ec2-user 0 May 12 01:03 task-r--r--r--. 1 root root 0 May 12 01:04 timers-rw-r--r--. 1 root root 0 May 12 01:04 uid_map-r--r--r--. 1 root root 0 May 12 01:04 wchanIs there a way to read the /proc//fd directory without using the root user? | How to read the /proc//fd directory of a process, which has a linux capability? | permissions;root;proc;not root user;capabilities | null |
_softwareengineering.55930 | I'm working on a piece of code which is free to use, but when a license code (or serial key or any other term like that) has been bought will remove some advertising. The code will be freely available as open source, probably under a GPL license, but of course I would rather not have people messing around with the code that verifies the license code with an external provider. Is there any way to legally protect this piece of code from being modified, or at least from being distributed after being modified, keeping the rest of the code open? | Licensing OS code, is it possible to protect certain blocks of code? | licensing;gpl;legal | null |
_unix.56602 | I have 53 gigabytes that need formating into /root, /swap, /usr/, /var, /home, and /tmp. If there's any help what is the best space allocation? Please let me know. | Partioning free space for manual install | linux mint;partition;system installation | For my 40GB SSD drive, I partition the swap partition to be the same as my memory (i.e., I have 2GB of RAM, so is the swap partition.) I reserve about 10GB for /root, and the rest goes to /home. For your case, I think:Swap partition as said14GB for /The rest for /homeI personally think partitioning for /usr, /var, and /tmp is too much trouble. |
_codereview.104240 | I was reviewing some WPF code I've written in C# last year.The scenario is the following:I've got a usercontrol that show usermessages and it's docked in the bottom of the application's workspaceI've got a ConcurrentQueue that receives message via a IMessageMediator (from Catel, but's irrilevant how data are pushed)I've a workerprocess that checks if there's some item in the queue and add them to a list that's bound to a gridprivate readonly ConcurrentQueue<UserMessage> queue;private readonly List<UserMessage> dataItems;private void worker_DoWork(object sender, DoWorkEventArgs e){ while (true) { if (!queue.IsEmpty) { UserMessage message; while (queue.TryDequeue(out message)) { dataItems.Add(message); } RaisePropertyChanged(() => FilteredDataItems); RaisePropertyChanged(() => ErrorCountMessage); RaisePropertyChanged(() => WarningsCountMessage); } Thread.Sleep(500); }}//That's used to show only filtered items (Error/Warning....)public IEnumerable<UserMessage> FilteredDataItems{ get { if (!enabledFilters.Any()) return dataItems; return dataItems.Where(x => enabledFilters.Contains(x.LogMessageType)); }}How can I remove this while(true) and the ugly/odd Thread.Sleep(500)? | Removing this odd while(true) for checking the queue | c#;wpf | null |
_webmaster.32587 | I have a domain name tradespring.net, and www.tradespring.net that redirect to my Heroku app with a CNAME record. However when I first try to access these sites it gives me a malicious warning.This is probably not the site you are looking for! blah blah blah then proceed anyways or back to safetyIts because my browser realizes that it is redirecting. How can I make sure anyone's browser (not just my browser) trusts this site and my Heroku app?I don't think i need an SSL certificate because this site is not sending sensitive info (credit card info, etc.). | How can I remove the security/malicious user warning from my website? | dns;heroku;cname | null |
_codereview.138228 | I want to convert my_long_variable to myLongVariable in sed.This works:echo my_long_variable | sed -r 's/(^|_)([a-z])/\U\2/g' | sed -r 's/^(.)/\l\1/g'Is there a more elegant way to do that with sed? | Transform snake_case to camelCase with sed | regex;sed | null |
_unix.325817 | I use grsecurity-hardened kernel and I can't get Systemback to work. On attempt to create backup it drops error: An error occurred while opening the following file: /etc/passwd I guess it could be permission restrictions. How to solve this in a best way? dmesg says nothing. also nothing in syslog.thank you. | Systemback and grsecurity kernel | linux;ubuntu;grsecurity | null |
_unix.110441 | I am using debian (unstable). My system was partitioning with 9 GiB for /. This is not enough for me and I use already 7,5 GiB.I don't want (for now) to use gparted in order to repartitioning (it takes a while and could be dangerous).Therefore, I am looking a way to see how much space softwares takes. I guess LaTeX takes a lot of space but, perhaps, I have (big) softwares installed which I don't need. I would like a list by size and I don't how to have this information. | How can I know how much space software takes? | debian;partition | null |
_softwareengineering.180234 | How would you implement / design a class which has to represent a bitmap?I'm stuck at handling the different possible color modes and I keep thinking that this should be somehow implementable using templates / design patterns in an elegant AND efficient way:Suppose you have a file.bmp. You then want to open that file to use it in your application:Bitmap myBitmap();myBitmap.open(file.bmp);The bitmap you just opened could have RGB colors, or it could be a grayscale image, or even a 1 bit per pixel image (i.e. black and white).In my application, I want to operate on the image (pixel) data. For example, I need some sort of brightness filter where I black out pixels whose (Red + Blue + Green) / 3 is below some filter value (i.e. 100).So I need access to the pixels:Pixel somePixel = myBitmap.pixelAt(10,30);But now I face the problem of NOT knowing what type of pixel this is. Of course, I could provide subclasses of Pixel (which then is an abstract base class) which ALL implement methods like getRGB(), getGrayScale(), ... where each subclass gives a way of converting between those colormodes (i.e. RGB to grayscale)But this feels ... hm, wrong.Do you know some good way to implement this?A nice feature I was thinking about is something like:myBitmap.getMode(); // A RGBMode object, RGBMode being a subclass of ModemyBitmap.setMode(new BlackWhiteMode()); // Converts the bitmap to a 1bpp imageAny ideas, recommendations, improvements?So the really hard part is to represent the different color modes, like RGB (8bit and 4bit), HSV, Grayscale, BlackWhite, ... without messing the applications code. | Encapsulate bitmap (*.bmp) as C++ class | design;c++;graphics | Depending on your processing needs, I'd go with either:a) A bitmap class that stores raw pixel data and format information; when loading, you resolve RLE compression, but otherwise leave the raw pixel values intact. Then add some methods to query the class for its pixel format, and possibly a getter/setter pair to transparently modify pixels in a format-independent way (i.e., convert to and from floating-point RGB representation on the fly). If you ever need to convert between pixel formats, you would do that in this model by loading the original bitmap, creating a new empty bitmap with the desired target format, and then copying pixels over through the floating-point RGB getters/setters.b) Store pixel data as RGB floats (or 16-bit integers, depending on the kind of transformations you want to do). When loading convert everything to that format, and then when saving, specify the target pixel format explicitly.Method a) has the advantage that some filters can be implemented in a completely lossless way, by using raw data and adapting the filter to the actual pixel format; it is more complicated to write such filters though, and if apply do more than one floating-point filter, you'll get more rounding errors on each pass (because you convert to and from integer every time).Method b) is easier to implement, especially because your filters only ever need to accommodate one pixel format, and it produces less rounding errors, but it does not allow for completely lossless filters (not even an identity filter: loading and then saving the same bitmap still introduces one round-trip's worth of integer-to-floating-point conversion errors). |
_softwareengineering.129164 | I'm wondering if I should use acronyms or initialisms when I list technical qualifications or mention specific technologies on my rsum or CV.For example:Entity Framework vs. EF vs. EF (Entity Framework)Graphical User Interface vs. GUI vs. GUI (Graphical User Interface)Is there a reason to prefer one version over another? Is it better to be as clear as possible, companies view not using the correct acronym a sign of lack of knowledge about the subject? | Should I use acronyms when listing technical jargon on my rsum? | resume | CV (Resume) searches today are performed exclusively by searching for keywords. So, the general rule of thumb is to never miss an opportunity to include in your CV any terms, keywords, buzzwords, etc which stand for technologies that you are familiar with, (and that you care to be hired to work on,) and to list them in all possible long forms, short forms, synonyms, abbreviations, etc.The good news is that each one of those forms only needs to appear once, and it needs to appear somewhere in your CV, but not necessarily in any prominent place. So, in the prominent places you should use the most appropriate terms (GUI, not Graphical User Interface, but Entity Framework, not EF,) and then hidden within the details you should expound on the jargon.By the way, when you feel you need to use both the long form and the abbreviation of a technology, the convention that a teacher of English would recommend is first the spelled out version, followed by the abbreviation inside parentheses. From that moment on, the teacher of English would recommend, you can continue using the abbreviation. |
_unix.165508 | This is my environment:Solaris Version 10; Sun OS Version 5.10 Oracle Version: 11g Enterprise x64 Edition.When I am getting log on through putty it is giving me this output:login as: ora Using keyboard-interactive authentication.Password:Last login: Sun Nov 2 10:24:21 2014 from abcIt is not showing $ sign or anything.. I can't write on it but cannot execute Linux command or get any output from it. I have even logged in by root password and yet still same. Can I one describe me this to me and guide this matter.My Oracle Based Database is running on it and I don't want to restart my server. So how can I fixed it and get $ or # ? | No $ or # Sign After Logging in Solaris 10 with Putty | ssh;solaris;putty | I have resolved the issue.The server was on hang state due to hardware failure.I let it remained logged in for more than 30 mins & it got the terminal.But thanks for the suggestions guys !! |
_softwareengineering.131814 | I'm looking at diving into Haskell for my next (relatively trivial) personal project. The reasons that I'm tackling Haskell are:Get my head into a purely functional languageSpeed. While I'm sure this can be argued, profiling that I've seen nails Haskell close to C++ (and seems to be quite a bit faster than Erlang). Speed. The Warp web server seems to be crazy fast in comparison to virtually everything else.So, given this, what I'm looking for are the downsides or problems that come along with Haskell. The web has a tremendous amount of information about why Haskell is a Good Thing, but I haven't found many topics about its ugly side (apart from gripes about its syntax which I don't care about at all). An example of what I'm looking for could be like Python's GIL. Something that didn't rear its head until I really started looking at using concurrency in a CPython environment. | Are there any downsides or problems with Haskell? | haskell | A few downsides I can think of:Due to the language's nature and its firm roots in the academic world, the community is very math-minded; if you're a pragmatic person, this can be overwhelming at times, and if you don't speak the jargon, you'll have a harder time than with many other languages.While there is an incredible wealth of libraries, documentation is often terse.Gentle entry-level tutorials are few and hard to find, so the initial learning curve is pretty steep.A few language features are unnecessarily clumsy; a prominent example is how record syntax does not introduce a naming scope, so there is no way to have the same record field name in two different types within the same module namespace.Haskell defaults to lazy evaluation, and while this is often a great thing, it can bite you in nasty ways sometimes. Using lazy evaluation naively in non-trivial situations can lead to unnecessary performance bottlenecks, and understanding what's going on under the hood isn't exactly straightforward.Lazy evaluation (especially combined with purity and an aggressively optimizing compiler) also means you can't easily reason about execution order; in fact, you don't even know whether a certain piece of code actually gets evaluated in a given situation. Consequently, debugging Haskell code requires a different mindset, if only because stepping through your code is less useful and less meaningful.Because of Haskell's purity, you can't use side effects to do things like I/O; you have to use a monad and 'abuse' lazy evaluation to achieve interactivity, and you have to drag the monadic context around anywhere you might want to do I/O. (This is actually a good feature in many ways, but it makes pragmatic coding impossible at times.) |
_unix.233799 | I powerwashed my device, so that it would be 'brand new,' but now I don't have sudo access. I am using a Toshiba Chromebook 1, which is a linux device. What is the default root password? | What is the default root password for a Toshiba Chromebook 1? | chrome book;toshiba | It looks like you should be able to access sudo without a password when no password is set. As stated from the linked source:By default, you can login as the chronos user with no password. This includes the ability to do password-less sudo.To access the virtual terminal press CTRL + ALT + =>. Where => is the right arrow key just above the number 3 on your keyboard (it should be F2).source |
_unix.234668 | My top looks like this: PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 6524 asjzdiwq 30 10 500m 41m 24m S 0.0 0.3 0:15.27 php-cgi 21274 asjzdiwq 30 10 500m 41m 24m S 0.0 0.3 0:04.97 php-cgi 9047 asjzdiwq 30 10 500m 40m 24m S 0.0 0.3 0:13.72 php-cgi 26918 asjzdiwq 30 10 499m 40m 24m S 0.0 0.3 0:12.87 php-cgi 13168 ahfvw0d1 30 10 498m 35m 20m S 0.0 0.2 0:03.49 php-cgi 8859 realnoni 30 10 495m 33m 20m S 0.0 0.2 0:11.27 php-cgi 6590 asjzdiwq 30 10 495m 32m 20m S 0.0 0.2 0:13.34 php-cgi 5657 holeyrai 30 10 495m 31m 19m S 0.0 0.2 0:04.47 php-cgi 14480 ripplecr 30 10 498m 31m 17m S 0.0 0.2 0:02.90 php-cgi 14442 ripplecr 30 10 497m 31m 17m S 0.0 0.2 0:02.00 php-cgi 10720 computer 30 10 496m 31m 18m S 0.0 0.2 0:08.75 php-cgi 23821 loghome 30 10 496m 31m 18m S 0.0 0.2 0:02.22 php-cgi 17623 devilsti 30 10 495m 31m 19m S 0.0 0.2 0:05.81 php-cgi 13305 realnoni 30 10 495m 30m 18m S 0.0 0.2 0:06.29 php-cgi 14461 ripplecr 30 10 496m 30m 17m S 0.0 0.2 0:01.47 php-cgi 8738 holeyrai 30 10 495m 30m 18m S 0.0 0.2 0:03.37 php-cgi 17569 devilsti 30 10 495m 30m 18m S 0.0 0.2 0:05.73 php-cgi 13174 ahfvw0d1 30 10 484m 30m 18m S 0.0 0.2 0:04.00 php-cgi 16126 realnoni 30 10 484m 30m 18m S 0.0 0.2 0:12.08 php-cgi 31561 a0w4pkbp 30 10 496m 30m 17m S 0.0 0.2 0:03.54 php-cgi 31565 ahfvw0d1 30 10 484m 29m 17m S 0.0 0.2 0:05.80 php-cgi 21275 asjzdiwq 30 10 484m 29m 18m S 0.0 0.2 0:01.77 php-cgi You can see that the same USER can have multiple COMMANDs running as php-cgi. I would like to find out which user is running the most processes and get a count of how many processes they are running. | Which user is running the most processes? | process;users;top | null |
_cogsci.8899 | I know how some music notes combinations sound pleasing, yet others do not. Does the same occur with different frequencies of light (colors)? Since spectral color and acoustic pitch are both defined by their respective wavelengths (frequencies), it made me think that the psychological properties of the two may be related. So do light waves, for example one with the same wave length as a mid-C and another with a mid-F wave, look nicely together? Or do certain colors when viewed simultaneously, or side by side, appear pleasing? | Acoustic and light wave coherency? | cognitive psychology;perception;color;hearing | First I have to say that the wavelengths of light are on a totally different order of magnitude than sound. So the parallel drawn in your question do light waves, for example one with the same wave length as a mid-C and another with a mid-F wave, look nicely together? may seem logical, but is on closer inspection not easily maintained. Instead, one way to address this question more appropriately would be to talk about wavelength differences; i.e., light with wavelengths differing X octaves compared to acoustic tones differing X octaves. Having said that I think it is worthwhile to sidestep the theoretical approach and take a closer look at how auditory and visual sensory information is actually processed at a neurophysiological level. Sound is processed in the inner ear (the cochlea), which basically works as a Fourier transformer, and specifically a frequency-to-place converter. The spatial distribution of the characteristic frequencies (the tonotopy) on the basilar membrane of the cochlea follows a pattern where one octave spans about 2.5 mm (Greenwood, 1990). For the approximately 10 octaves the human ear can hear (~20 Hz - 20 kHz) we have 16,000 inner hair cells. See the following picture for a rolled-out cochlea with the tonotopy illustrated:source: what-when-how.com The eye, on the other hand, analyzes light frequencies using just 3 colors (red, green, blue) by means of three cone classes (as opposed to 16,000 hair cells each sensitive to a slightly different acoustic frequency). Although the visual system does a great job in combining this sparse frequency information into a spectrum of colors, it is not a frequency analyzer as such. In fact, it is more of a frequency combiner, as it combines the ratios of activation of the cone classes and runs it through a system of color opponency. By weighing the relative contributions of the three colors (RGB) using the opponent system (R-G, Y-B) the visual system estimates the color of the object you are looking at. Below on the left is illustrated the spectral frequency sensitivity of the three cone classes (note the unequal, non-octave distribution of the three across the dynamic spectrum range), and on the right the color-opponent (Hering) model. source:huevaluechroma.com and giantitp.comThe opponent nature of human vision (blue-yellow and red-green axis) results in a 2-dimensional color space which is very different from the 1-dimensional frequency space of the cochlea (Mather, 2006). Note that the third visual dimension is brightness, comparable to the second dimension of loudness in the ear.In all, based on a neurophysiological signal-processing point-of-view, hearing and seeing frequencies are two completely different things. Comparing octaves between the two is worse than comparing apples and oranges, as apples and oranges share at least the same dimensionality. It probably doesn't answer the question, but it may answer the question why it cannot be answered in any logical, comprehensive and straightforward way without loosing oneself in subjective monologues about I like this and this combination of timbres but I don't like this color combination so much kind-of-thing. Admittedly, it can be experimentally addressed by inquiring about the subjective 'pleasantness' of a set of combinations of colors and pitches in a study population. But from a physical and pysiological perspective, comparing the two entities of light and sound through equal-octave comparisons doesn't make sense since: (1) the two entities are processed through completely different neurophysiological principles as described above, ('1D acoustic frequency Fourier analyzer' versus '2D spectral combiner'), and (2) they represent entirely different physical entities altogether (photons/EM waves versus air pressure differences). Their only commonality is that they have an oscillatory nature, but that's where the parallel starts, and ends. ReferencesGreenwood et al. JASA 1990; 87:2592-605Mather. Foundations of Perception 2006 |
_unix.192772 | I am deploying a single Laptop via PXE boot over a wired network.It runs perfectly, DHCP connects, TFTP finds and loads config data, scsi sends over the boot partition. Then it pauses for a minuteLooking at the dmesg logs, there is a 62 second gap before the scsi initiator starts to try to load the root partition. This happens every time. The other scsi-ahci connections have started up fine, but the iscsi initiator just hangs. Looking at tcpdump, there is no communication during this period.What is going on here? Can I remove this waiting period?The host server is running RHEL Server 7, and it the only other thing on the network besides the laptop (literally a single copper cable). | PXE Boot iSCSI wait time | pxe;iscsi | null |
_unix.182231 | On Ubuntu and Debian, often if I try to run a program I will get a message that says something to the effect of: You don't have that program. To get it type sudo -apt -get -install programName(or some variation on that). Then I usually type exactly the command that was just suggested. Is there a hotkey that will automatically type the suggested command for me, e.g., I type something like AltUp and sudo -apt -get -install programName is automatically typed? | Hotkey for doing sudo suggestions | sudo;keyboard shortcuts | Just follow this link to bind commands.https://stackoverflow.com/questions/4200800/in-bash-how-do-i-bind-a-function-key-to-a-commandBind to any key you want: sudo apt-get -install !:0!:0 is the last command run, !:1 the first param, etc. !! is the last command line. This is all buried in the bash docs.Hope that answers everything.Caveat: I tested this code with echo !:0 not sudo apt-get -install !:0 for obvious reasons. I ran ls first and then pressed the F1 key (where I bound it). I got it to say echo !:0, then expand to echo ls, and then write the letters ls to the terminal. I see no reason why this won't work for you though. |
_softwareengineering.222464 | I need to design an online exam server for an exam like GRE in which question difficulty increases if you answer correctly and decreases if you answer wrong.Questions are multiple choice questionsDifficulty scale of question is 1-10, 1 being the easiest and 10 being the hardest.If two continuous questions are answered wrong, decrease the difficulty by 1 and if two questions answered right increase the difficulty by 1.Test starts with a question of difficulty level of 4.Question carries marks equal to its difficulty.My question is Which the data structure should I use to store the questions, and best algorithms to fetch the question by its difficulty, etc. ?Currently what I'm thinking is I'll be having a double link-liststruct node {int data;node *prev;node *next;int nint MAX;};here 2 n's we need to store... one is MAX (actual size) and n is possible random size to pick questions from n - MAX we selected alreadyfor each double linked list you can add extra int data where u can storeprev link, next link, pointer to array, int Maxdata(MAX size), int n(current size)Each node is a pointer to array where list of questions for each level.if answer correct it moves next node and pick the random questions from that list else move to previous node and pick questionFor eg- lets an array is having 10 questions 1 - 10. so array size is n = 10 you know that.now you selected a random question rand() % 10 = 6 th questions.now swap the question number 6 & 10, make n-- and return the 6th question.now n = 9 so next time 10th will not be considered.random will return 1 - 9 onlyIs there any better way of doing it? | Designing online exam | design;algorithms;data structures | null |
_webmaster.31997 | I can remember that some years ago several providers advertised the possibility to use the @ syntax instead of general subdomains with their DNS service. Today, I can't find any documentation or hints about this anymore, besides Google Chrome asking me whether I wanted to open http://[email protected] when entering the possible email address (without the protocol) in the search bar. What happened to this domain syntax? | What happened to the [email protected] syntax? | domains;dns;domain registrar | @ has a special meaning, when used in a URL. Here's a URL with everything possible in it:scheme://username:password@domain:port/path?query_string#fragment_idThe @ separates the password from the domain. So I think you're remembering something else. |
_webmaster.60171 | On my DEV server, after a user finishes a game on the website, a semi-transparent overlay covers the whole page. The score is then shown on the overlay. Through the overlay, you can still clearly see where google advertising would go. There is no way to accidentally click it. In fact, the advert is not clickable until the overlay is closed (and it is not possible to accidentally click the advertising when clicking close).I've read the Google Adsense Policies and suspect that I am violating the following policyGoogle Ads may not be:Obscured by elements on a page.The picture below shows you the overlay and advertising.It seems the answer is pretty cut and dry, but I'm weakly hoping that by obscure they mean you can't see the advertising at all. Anyway, I'd like to see what other peoples' take is on this. As you can probably guess, for aesthetic reasons I'd really like to leave the overlay in place.UPDATE:Just to be clear, I'm not using Adsense for Games. I'm using the Adsense meant for websites. | Does a semi-transparent overlay that only appears temporarily at game completion violate Google Adsense policy? | google adsense;advertising | I've seen this question asked many times in various forums. The answer is not clear.Here is a blog post where somebody posed the question to their Google ad rep:Is Lightbox is allowed with AdSense? So I shot a quick email to my Google AdSense Representative. After reviewing the sample page I provided, the AdSense representative finally sent me good news.Yes, you can use Lightbox and Google AdSense ads together on a web page without any problem. One important thing though, AdSense ads cannot not be shown in the Lightbox pop-up!Here is a Google Product Forum that says that lightboxes are OK, as long as they fill the whole screen and don't use transparency: https://productforums.google.com/d/msg/adsense/ngldkoLNIho/eInO41RpcZwJOther times when asked the answer is strictly prohibited:https://productforums.google.com/d/msg/adsense/RABJE01xqQ0/Tu6JZNsac_IJhttps://productforums.google.com/d/msg/adsense/NJRVYzKQ_Tg/cQr5BnxFnYoJhttps://productforums.google.com/d/msg/adsense/TgKGGhfJQag/D6TmwoFLvmoJ |
_webmaster.1562 | I have a Windows VPS hosted at some web host, I have remote desktop administrator access and I can install whatever software I need on that VPS.This is a basic low cost VPS, so the system resources (especially memory) are extremely limited, the main difference between backing up a dedicated server and a VPS is the VPS's limited resources.My requirements are:Backup the VPS content (I don't want to backup the entire virtual hard drive, I want to be able to access my files without installing the same VM software).Backup files, IIS configuration and SQL Server databases.Extremely light weight, use (almost) no memory when inactive, able to limit memory usage when backing up.Backup to a remote location (Amazon S3 is best because it's cheap).Fast and bandwidth efficient (uses compression, incremental backup, etc.)Optionally able to backup up mail server (I use SmarterMail), I can live without this because I have a relatively simple e-mail setup and I keep all my messages on my desktop in Outlook.Backing up files in use is not an issue for me because most files (except SQL Server and mail data listed above) will never be locked on this specific server.I have a limited budget, obviously I would love a free solution ,but this is a business machine and good backup is worth some money. | What are the best options to backup a hosted windows VPS | vps;backups | null |
_vi.4309 | I think it would be very nice if I can check whether current vim was compiled with python support, instead of having error message popping out every time vim is launched.Can this check be done in vimscript?Note that running shell wouldn't work if multiple vim's are installed and user launch one of them:vim --version | grep -q '\+python\>'It would be considered as a better approach if it could be checked within vimscript alone. | How to check with Vimscript whether python support is enabled? | vimscript | How aboutif has('python') ...endifSee :help has() and :help feature-list at list item 1 and /python. |
_unix.358720 | I would like to install squid proxy with SSL bump, I am working on my Virtual lab and once everything is ok I will Test it on the real network. I already created I directory for the cert and generated the cert as below:#Generate Private Keyopenssl genrsa -out MSY.com.private 2048 # Create Certificate Signing Requestopenssl req -new -key MSY.com.private -out MSY.com.csr# Sign Certificateopenssl x509 -req -days 3652 -in MSY.com.csr -signkey MSY.com.private -out MSY.com.certthen I fill the info and put the 'Common Name' something other than the domain or server_name. in addition, please find the below lines from the squid configuration file:http_port 3128#the problem is with the below linessl-bump cert=/etc/squid/ssl_cert/MSY.com.cert key=/etc/squid/ssl_cert/MSY.com.private generate-host-certificates=on version=1 options=NO_SSLv2,NO_SSLv3,SINGLE_DH_USE# SSL Bump Configssl_bump stare all ssl_bump bump all and its not working and if I remove the SSL bump certificate line from the configuration, the proxy works but without SSL. my questions can we eliminate SSL-bump from configuration and can I manually copy the certificate to the client/user machine and added to his/her Internet browser.also i check the journalctl -xe and found the below error:/etc/squid/squid.conf:3 unrecognized: 'ssl-bump'any ideas ? | Squid proxy with ssl-bump - unrecognized: 'ssl-bump' | centos;openssl;squid;x509;ssl bump | null |
_unix.306558 | Does anyone know if find command do full disk scan if I apply -mtime +30? I am worrying that when number of directory grow, it will become deadlock whenever I run find, and trying to find a way to limit number of directory it search, but not sure even define mtime would still search for every directory. | does find command do full disk scan if apply -mtime +30? | linux;shell;find | find will scan a directory tree (this is not necessarily a full disk).By default, find will examine directories to return every file in the hierarchy. TESTS (such as -mtime) do not modify which files are returned. Unless combined with some ACTION (like -prune or -quit), the mod times of the files won't affect the search space.The various OPTIONS, TESTS, and ACTIONS are outlined in the man page.I am worrying that when number of directory grow, it will become deadlock whenever I run find, and trying to find a way to limit number of directory it searchI'm not sure why deadlock is a worry. As the files increase, the amount of work find has to do increases as well. But it should always complete. Unless you have some information about which files in your hierarchy may or may not match, neither find nor the filesystem can help. The only way to print every possible match is to examine every possible file.Now if you have some information that can limit which ones are possible, you might be able to add in some actions that reduce the work that is done. |
_softwareengineering.157202 | How do you debug PHP? Just with debug-prints in your script? Or is it worth installing XDebug? Is there any better debugging possiblity? | Debug PHP: is XDebug worthwhile? Are there any alternatives? | php;ide | null |
_reverseengineering.11350 | Maybe someone could help me with the following problem:I have an interesting byte sequence that I found within a MIPS ELF binary that exists on the hard drive. This byte sequence may be, for example, 9c 6c 3c 04 80 2d 24 84 85. Now I want to find this byte sequence with IDAPython. Therefore, I use the idc.FindBinary() function like so:address = idc.FindBinary(0, SEARCH_DOWN, byte_sequence)which finds the first occurrence of the byte sequence at address. In general I want to achieve two things:I want to colorize the effected affected lines in the IDA ViewI want to get the disassembled instructionsCurrently there are two subproblems I want to solve:The byte sequence may start within the instruction, for example, in a jal address the byte sequence starts at address instead of at jal. How can I search backwards to find the beginning of the instruction when the byte sequence started within the instruction? Colorizing works with:SetColor(address, CIC_ITEM, 0x208020)If the byte sequence is 9 bytes long (as in the example above), how can I tell IDAPython to disassemble all 9 bytes. I would have to know how long the instructions are that IDAPython disassembles to get to the next instruction. What I know is that I can disassemble at a single addresses with:disasm = idc.GetDisasm(address)Any help would be greatly appreciated! | Colorize and disassemble byte sequences with IDA Pro and IDAPython | ida;disassembly;idapython;binary | You can easily do that using Sark:# Get all the lines relevant to your bytesfor line in sark.lines(start=address, end=address + len(byte_sequence)): # For each line, color it, and print the disasm and the instruction length line.color = 0x123456 print 'Line Size: {}\nLine Disasm: {}'.format(line.size, line.disasm)You might need to add handling for cases where there is no disassembly (the bytes are data-bytes and not code). |
_softwareengineering.157841 | I currently developing some M2M-transformations with the Atlas Transformation Language (ATL).During studying the language constructs and properties I have often read, that ATL is a prototype for QVT, but was not used for QVT. This leads me to the question, if ATL is a deprecated language.Personally, I claim that ATL is not deprecated because there are some indications for this:If I look at the website of ATL the last Update was August, 26th 2011. The first specification of QVT was 2008. So I think the development of ATL seems to proceed.There are also some papers since 2011 on google scholar:http://scholar.google.de/scholar?q=atl+m2m&btnG=&hl=de&as_sdt=0&as_ylo=2011It is still part of the M2M-frameworks of EclipseWhat would you say? Would it be better to user another M2M language or is ATL future proof? If not, do you know possibilities to transform ATL into other M2M-languages? | Is ATL a deprecated language? | programming languages;modeling | null |
_webapps.46623 | After my Company switched to Office 365 yesterday, I've found that the font for the list of messages for the new Office 365 webmail is too big.As you can see from the image below, you can barely see 3-4 messages without the need to scroll.Is there a way to make that font smaller? I've searched all the options without success. | Font size in message list for the Office 365 webmail | outlook on the web | null |
_unix.378911 | I was doing some research on some C functions, and I noticed when I used, for example, man fgets, it outputs the manual for the fgets function; however, it references ISO C99 which is out-of-date compared to ISO C11. Is it possible to update manuals within terminal, not just particularly C manuals? | Is it possible to update manuals on MacOS | osx;man | null |
_codereview.4148 | I needed a mutable priority queue (the priorities can be changed) for my currect project, and started by simply wrapping a class around a std::vector and make/push/pop_heap. However, it is not nearly fast enough, profiling shows ~70% of processing time is spent in the queue. I need some input on how to either fix the queue, or if there already exists something which can do this but better (there is a mutable_queue in boost, but in the pending directory, for instance).template <typename ValueT, typename KeyT>class UnconsistentQueue { struct Elem { Elem(const ValueT& v_, const KeyT& p_) : v(v_), p(p_) {} bool operator<(const Elem& rhs) const { // Note that this is reversed, since we want a lowest-first prio queue return rhs.p < p; } ValueT v; KeyT p; };public: typedef typename std::vector<Elem>::iterator iterator; typedef typename std::vector<Elem>::const_iterator const_iterator; void push(const ValueT& v, const KeyT& p) { q.push_back(Elem(v, p)); std::push_heap(q.begin(), q.end()); } void update(const ValueT& v, const KeyT& p) { update(v, p, q.begin()); } void update(const ValueT& v, const KeyT& p, const_iterator hint) { iterator i = q.begin(); if(hint->v == v) std::advance(i, std::distance<const_iterator>(q.begin(), hint)); else { for(; i != q.end(); ++i) { if(i->v == v) break; } } if(i != q.end()) { i->p = p; std::make_heap(q.begin(), q.end()); } } void pop() { std::pop_heap(q.begin(), q.end()); q.pop_back(); } const ValueT& top() const { return q.front().v; } const KeyT& top_key() const { return q.front().p; } const_iterator begin() const { return q.begin(); } const_iterator end() const { return q.end(); } const_iterator find(const ValueT& v) const { const_iterator i; for(i = q.begin(); i != q.end(); ++i) { if(i->v == v) break; } return i; } void remove(const ValueT& v) { const_iterator i = find(v); if(i != q.end()) { q.erase(i); std::make_heap(q.begin(), q.end()); } } bool empty() const { return q.empty(); } void clear() { q.clear(); }private: std::vector<Elem> q;};In my project, the key type is encoded in this struct:template <typename CostType>struct Key { bool operator<=(Key<CostType> rhs) const { return (k1 <= rhs.k1) || (k1 == rhs.k1 && k2 <= rhs.k2); } bool operator<(Key<CostType> rhs) const { return (*this <= rhs) && !(rhs <= *this); } CostType k1; CostType k2;};(The paper which defines the algorithm only defines a <= operator, but I need a strict weak ordering, so I implemented it like this. Good?)Below is the relevant part of the profiling results as generated by AMD CodeAnalystCS:EIP Symbol + Offset 64-bit Timer samples 0xf156c0 Key<double>::operator<= 14.45 0xf1c350 std::_Adjust_heap<UnconsistentQueue<unsigned int,Key<double> >::Elem *,int,UnconsistentQueue<unsigned int,Key<double> >::Elem> 7.29 0xf140d0 Key<double>::operator< 6.91 0xf1d260 UnconsistentQueue<unsigned int,Key<double> >::Elem::operator< 6 0xf1c250 std::_Push_heap<UnconsistentQueue<unsigned int,Key<double> >::Elem *,int,UnconsistentQueue<unsigned int,Key<double> >::Elem> 5.64 0xf15910 std::_Vector_const_iterator<std::_Vector_val<UnconsistentQueue<unsigned int,Key<double> >::Elem,std::allocator<UnconsistentQueue<unsigned int,Key<double> >::Elem> > >::operator!= 4.56 0xf16570 std::_Vector_const_iterator<std::_Vector_val<UnconsistentQueue<unsigned int,Key<double> >::Elem,std::allocator<UnconsistentQueue<unsigned int,Key<double> >::Elem> > >::operator== 4.27 0xf15160 UnconsistentQueue<unsigned int,Key<double> >::find 4.01 0xf16130 std::vector<UnconsistentQueue<unsigned int,Key<double> >::Elem,std::allocator<UnconsistentQueue<unsigned int,Key<double> >::Elem> >::end 3.99 0xf1b0b0 std::_Make_heap<UnconsistentQueue<unsigned int,Key<double> >::Elem *,int,UnconsistentQueue<unsigned int,Key<double> >::Elem> 3.21 0xf16a90 std::_Vector_const_iterator<std::_Vector_val<UnconsistentQueue<unsigned int,Key<double> >::Elem,std::allocator<UnconsistentQueue<unsigned int,Key<double> >::Elem> > >::_Vector_const_iterator<std::_Vector_val<UnconsistentQueue<unsigned int,Key<double> >::Elem, 2.97 0xf15b50 std::_Tree<std::_Tmap_traits<unsigned int,double,std::less<unsigned int>,std::allocator<std::pair<unsigned int const ,double> >,0> >::_Lbound 2.93 0xf16540 std::_Vector_const_iterator<std::_Vector_val<UnconsistentQueue<unsigned int,Key<double> >::Elem,std::allocator<UnconsistentQueue<unsigned int,Key<double> >::Elem> > >::operator++ 2.41 0xf1c240 std::_Move<UnconsistentQueue<unsigned int,Key<double> >::Elem &> 1.86 0xf16500 std::_Vector_const_iterator<std::_Vector_val<UnconsistentQueue<unsigned int,Key<double> >::Elem,std::allocator<UnconsistentQueue<unsigned int,Key<double> >::Elem> > >::operator* 1.81 15 functions, 408 instructions, Total: 120448 samples, 72.33% of shown samples, 32.53% of total session samples | Slow mutable priority queue | c++;performance | The standard already has a priority queue.std::priority_queueInternally it uses std::vector<> (by default) but the elements in the vector are organized into a binary tree structure for faster sorting and organization. (ie element 0 is the root, element 1,2 are children of 0 etc).If you want to do this manually you can your own container and the following methods:Push HeapPop HeapMake HeapSort HeapThe problem with the heap structure it only really supports removal of the head node. Once you start deleting nodes in the middle you need to re-build the heap manually (which seems to be your problem). According to the documentation re-building the map is linear (up-to 3n plus your linear traversal so 4n) so O(n).So it does not look like you really want a priority queue. What you really want to use is the std::map. This allows O(log(n)) insertion and deletion of elements anywhere in the map and the container is maintained in sorted order (using strict weak ordering). So you can iterate over the map in order if required.Also once elements are in the container there is no further copying of the elements. In the priority queue the elements were copied around the vector and if the copy construction of the key/value was expensive then other operation would suffer.Of course there will be a cost in using a map which is the extra memory it will use (a vector is very efficient in terms of memory usage). |
_webapps.24023 | I would like to make a page on my site where I merge all the photos from different Facebook page's albums. Of course, after I have been approved by them (somehow), to grab their photos when they upload on facebookI'm thinking to do this through RSS feeds?Can I do this? Does Facebook allow such option? What should I look into?I'm not sure if its possible, just something I have imagined could work out good.I would like to be a site, that is a 'collector' of multiple facebook page's albums photos. And I sync with the rss feeds I will grab the uploaded photos (links?) in the rss feed from the facebook page. | Facebook page photos RSS | facebook;rss | null |
_unix.361685 | I am trying to save a users home directory to a users.txt file, but I just keep saving my own. The script asks the user to enter their username, which I have saved in $username. When I runls ~ >> users.txtIt shows ls home/student/am1014 (which is my username)I assume I need to use sudo to store it but I'm not sure how. | Sudo as another user to save their home directory address to a txt file | scripting;sudo;users | null |
_unix.53692 | It just seems there should reasonably be something like this considering so many folks run *nix on laptops and laptops have such consistent hardware sets. At a guess I'd imagine there's likely in the ~1000-2000 range of hardware combinations making up ~85% of laptops in current use (this is completely random guess off the top of my head).That said, does anyone know of any sites where people share their precompiled kernels or .configs? I used to meddle them up myself; but that was ~10 years ago and I don't frankly want the headache of getting my hardware working myself. Would be awesome if I could just go to a website, start selecting hardware my machine has and it filters down to other peoples shared .config files, or I could just put in my laptop's model number and it finds someone elses posted .config who had the same.On a side note, yes the common default kernels distros come with seem to work fine on my laptop, but I'm struggling to get the ATI drivers working correctly (I understand I need to remove DRI/KMS and stand on my head while doing some other things; so far I've managed to boot to a black screen in my latest kernel recompile attempt) but it seems somebody else has probably wrestled this into submission on their machine, and their should be a site they can share it in a more concrete form than tutorial. | Is there any sort of online kernel repository or sharing sites (possibly for laptops) | kernel;repository | null |
_unix.111093 | I have one problem with my date format. I want to change from one format to the other and vice verse. My date formats are:Format1 : 1/24/2014 Format2 : Jan 24 How can I do this? | Convert a date format | command line;date | null |
_softwareengineering.175121 | Some time ago I have read two different books and each of them gives totally different answer for the question if it is a good pattern to define constant values in the interface (in java).So I am curious of your opinions with some reasonable arguments.Is it a good habit/ pattern to define constant values in interfaces in java?Is it generally good, generally bad or it depends? | Constant values in the interface | java;design patterns;clean code;design | Item 19 of Effective Java 2nd ed. recommends the following:If the constants are strongly tied to an existing class or interface, you should add them to the class or interface...If the constants are best viewed as members of an enumerated type, you should export them with an enum type. Otherwise, you should export the constants with a noninstantiable utility class.public class SomeConstants { private SomeConstants() { } // Private default constructor public static final double WEIRD_NUMBER = 123456.7; public static final int ANOTHER_NUMBER = 5;}Edit: As with all things, exceptions exist. This case (constants and some methods need to be shared by external types) might be a good argument for using an interface in this manner. |
_unix.355126 | I did see this question on other threads - but I'm going to be a bit more specific.Let's say I would like to take the Debian base (stable) and then rename it and add some own repos (and packages). How do I then generate an ISO image properly? How do I modify the installer?I just wan't to learn - not anything too professional. | How do you create a Linux ISO? (Debian fork) | debian installer;debian cd | null |
_unix.185089 | I have a problem, during write something into a root file:$ ll /sys/bus/usb/devices/3-2/power/wakeup-rw-r--r-- 1 root root 4096 Feb 16 17:28 /sys/bus/usb/devices/3-2/power/wakeup$ sudo echo disabled > /sys/bus/usb/devices/3-2/power/wakeupbash: /sys/bus/usb/devices/3-2/power/wakeup: Permission deniedeven it did not ask me for password. How can I solve this?Why I can't use sudo directly? | sudo issue during echo something to a root file | sudo;echo | You cannot use sudo with redirection, because the redirection is done by your original shell which runs as your own user code. It tries to set up a file descriptor for the file mentioned after the >, which fails as your user is not able to write to it.Costas's method works, as does spawning a subshell:sudo sh -c echo disabled > /sys/bus/usb/device/3-2/power/wakeup |
_softwareengineering.17710 | A question on software specialties inspired this question.How valuable is a software generalist compared to a specialist? When I say generalist, I mean someone who can take a project from requirements to deployment, and is competent with all phases of the software development lifecycle. Someone who can put all the specialties together into a cohesive whole. An expert generalist knows his or her weaknesses and fills them by relying on specialists - example: Oracle specialists or UX specialists.What do you see as the ultimate career path of the software generalist? | What is the career path for a software generalist? | career development | The ultimate career path of the software generalist is to become the one person IT army, able to take on any problem involving code of any kind as a self-employed mercenary. I'd imagine such people would be extremely rare, but they may exist somewhere. ;)The generalist may have the challenge of maintaining their skill set as I'd imagine most people in this role would end up specializing a bit in terms of what they experience as it isn't often that a company would give the same guy the opportunity to know every kind of system,e.g. CRM, ERP and CMS to name a few by acronym. There are various points between the generalist and specialist though as something like web development could be seen as being rather general or rather specialized depending on one's view. |
_unix.110463 | After installing Kali with the Nuke feature I'm wondering if there's an easy way to limit failed login attempts by simply erasing the LUKS keys-lots.EDIT: I'm asking with the idea in mind to store the password - with some random strings inside and besides it or in some other creative way - in front of the computer monitor. | Auto-delete LUKS Key-slots | luks;kali linux;privacy | null |
_codereview.9233 | Here it is at work: pcsn.nnja.coAs you can see, while the slider .shuffle works and is adjusting itself as it was intended to when the corresponding navigational item #menu-main-navigation li a is hovered upon, the effect is a bit erratic with abrupt mouse behavior.My jQuery is located in the head:$(document).ready(function() { function initializeCycle(){ $('.shuffle').cycle({ // Slider element timeout: 6000, // Change slide every 6 seconds speed: 1000, // Transition should last 1 second fx: 'fade', allowPagerClickBubble: true, // Allow navigation to remain clickable pager: '#menu-main-navigation', // Navigation element pauseOnPagerHover: true, pagerEvent: 'mouseover', pagerAnchorBuilder: function(idx, slide) { // This selects existing anchors within main nav items // and sets them as the pager children return '#menu-main-navigation li:eq(' + (idx) + ') a'; } }); }; initializeCycle();});How would I improve this? I have a solution that works, but it's sloppy.Ideally, cycle's speed option would asynchronously adjust to zero upon hovering over navigational items, so that the fade effect on the transitions of the slider are instant and the erratic behavior is prevented.This is my unfinished logic to do this:$(#menu-main-navigation).bind(mouseenter mouseleave, function(event){ // Set the 'speed' option in cycle to 0 when an item // in the main navigation is hovered upon so that it // 'snaps' in its transition rather than fades});Am I going in the right direction? | jQuery cycle slider | javascript;jquery | A cursory glance at the plugin's documentation yielded this example, which seems close to what you're aiming for. Alas, no fade...Anyway, I tinkered a little with it, and this works. It's not elegant, but that's mostly the plugin's fault...$(function() { $('#slideshow').cycle({ fx: 'fade', speed: 1000, timeout: 6000, pager: '#nav', pagerEvent: 'mouseover' }); // retrieve plugin data (i.e. the speed params) var data = $('#slideshow').data('cycle.opts'); // bind navigation mouseenter to increased speed and vice versa $('#nav').bind('mouseenter mouseleave', function(e) { if (e.type == 'mouseenter') { data.speedIn = 100; data.speedOut = 100; } else { data.speedIn = 1000; data.speedOut = 1000; } });});Also, lose the InitializeCycle(), right now it's just a useless wrap. Maybe consider using a different plugin altogether. Oh, and one more thing: nice page design!PS: It's better to put the scripts at the end of the document. |
_webapps.37622 | I've seen the following post from at least two of my Facebook friends in the last couple of days (and who knows how many more I've missed when I've been off line).I think I understand the logic behind the request - basically the theory is that your comments and likes of your friends posts won't become public.However, I'm sceptical that this is a real thing and not something that gives us apparent control over what the world can see but in reality doesn't do anything.Hi, FB friends: I want to stay PRIVATELY connected with you. I post shots of my family that I don't want strangers to have access to!!! However, with the recent changes in FB, the public can now see activities in ANY wall. This happens when our friend hits like or comment ~ automatically, their friends would see our posts too. Unfortunately, we can not change this setting by ourselves because Facebook has configured it this way.PLEASE place your mouse over my name above (DO NOT CLICK), a window will appear, now move the mouse on FRIENDS (also without clicking), then down to Settings, click here and a list will appear. REMOVE the CHECK on COMMENTS & LIKE and also PHOTOS. By doing this, my activity among my friends and family will no longer become public.Now, copy and paste this on your wall. Once I see this posted on your page I will do the same. ThanksSo - will this do what it purports to? | Will this method for apparently restricting what people can see on Facebook actually work? | facebook;privacy | null |
_webapps.65774 | How can sync I my Twitter and Stack Exchange accounts together so that the questions and answers that I post to all of Stack Exchange sites are auto tweeted to my Twitter? | Is it possible to sync questions and answers that I post in all of Stack Exchange site to Twitter? | automation;twitter integration | null |
_cs.50090 | I am wondering why data fragmentation is a problem on main memory.On a software level, virtual addresses are used anyway. So why can one address space not be split up into multiple segments, like a hard disk might do? I don't see how the performance would be affected, as the time needed to access memory addresses does not vary. Is this just a limit of the MMU?In other words, my question is why does a process need continuous memory segments? For example:Process D requests a memory block that could fit into the two free segments, if the block were split into two pieces. Why can't this be done?It would be great if you could add a source so I could read more about this topic, if you have one. | Why is data fragmentation not possible on main memory (RAM)? | memory hardware;virtual memory;memory allocation | [Disclaimer : I probably don't actually understand the question]-DRAM access time is not constant, as memory is physically arranged in rows, columns, banks. It is beneficial to limit fragmentation of actual memory.-On multi-cpus hardware, memory can also have different access times (NUMA), so the OS needs to avoid putting programs at random.-The physical address range can be not contiguous, it may be hidden by hardware mechanisms, or managed by the OS. For example a computer equipped with 8 slots for 4GB memory modules, can use a fixed 4GB address for each module, and if 1GB modules are installed, there are 3GB holes every 4GB. MMUs can effectively hide to application software how memory is allocated. Each page (page size is often 4kB) can be mapped to actual memory, only on disk, or unitialised, several pages initialised to zero can be allocated to the same physical memory, several applications can share the same physical memory for code and nonmodified data...So ?When a process does a malloc() for a 1MB array, the stdlib/OS will eventually return a pointer to a 1MB area of virtual memory. It is typically split into around 256 pages of 4kB. These 256 pages may be placed at random in the physical RAM, or maybe don't even exist until the process eventually accesses them. The OS maintains memory allocation structures for identifying which memory is used by what, and page tables for the MMU to perform virtual to physical translations.(Note : Pages are not always 4kB on all architectures, some MMUs expect software management of virtual to physical translation instead of directly accessing tables, a.k.a. tablewalking) |
_softwareengineering.164752 | I am currently building a test plan for the system I am working on. The plan is 5,000 lines long and about 10 years old. The structure is like this:1. test title precondition: some W needs to be set up, X needs to be completed action: do some Y postcondition: message saying Z is displayed2. ...What is this type of testing called ? Is it useful ? It isn't automated.. the tests would have to be handed to some unlucky person to run through and then the results would have to be given to development. It doesn't seem efficient. Is it worth modernising this method of testing (removing tests for removed features, updating tests where different postconditions happen, ...) or would a whole different approach be more appropriate ? We plan to start unit tests but the software requires so much work to actually get 'units' to test - there are no units at present ! Thank you. | Resurrecting a 5,000 line test plan that is a decade old | testing;unit testing | From what you write, it looks like a list of test cases for manual integration testing / GUI testing. It might not be efficient, but any tests are better than no tests and any plan is better than no plan, so you might as well start with what you have.Certainly you would need to review the plan and update it to cover changes made to the software over time. Obviously having obsolete test cases for nonexistant functionality would be counterproductive.Keep in mind that even though this test plan was written with manual testing in mind, you might as well automate the process. Research automated testing tools available for your project/platform. If it's a web application, look into Selenium. There are solutions for desktop applications too, but I'm not familiar with any to make a suggestion. Even though it may be a time consuming task, automating these tests, you may find it easier then introducing unit tests. You may also find it useful to have these automated tests when you get around to refactoring the project, as you can use them to validate your changes while you're adding the unit tests. |
_webmaster.77144 | As you will see from the screenshot attached there is a clear discrepancy between the number of impressions and the lack thereof clicks, thus no CTR data. I know WMT dont give you the full amount of data but this is giving me zero clicks for brand related terms.Ive just started with this company so I dont know if it was always like this. | Google Webmaster Tools showing no clicks on any queries | seo;google search console;clicks | You can troubleshoot this by comparing GWT report with your Audience -> All Traffic -> Channels report. If your organic traffic didn't change dramatically during the time in questions then its a GWT issue. |
_unix.323045 | I pressed Mod+S and my windows flatted into a stack of bars. How can I undo this action or expand them back into their original configuration? The best route I found was to individually select each window and to Mod+Shift+arrow key to split horizontally. Surely there's a trick I'm missing? | How to unstack windows | i3 | null |
_softwareengineering.28113 | I've just started working on a project and we're using domain-driven design (as defined by Eric Evans in Domain-Driven Design: Tackling Complexity in the Heart of Software. I believe that our project is certainly a candidate for this design pattern as Evans describes it in his book.I'm struggling with the idea of constantly refactoring.I know refactoring is a necessity in any project and will happen inevitably as the software changes. However, in my experience, refactoring occurs when the needs of the development team change, not as understanding of the domain changes (refactoring to greater insight as Evans calls it). I'm most concerned with breakthroughs in understanding of the domain model. I understand making small changes, but what if a large change in the model is necessary?What's an effective way of convincing yourself (and others) you should refactor after you obtain a clearer domain model? After all, refactoring to improve code organization or performance could be completely separate from how expressive in terms of the ubiquitous language code is. Sometimes it just seems like there's not enough time to refactor.Luckily, SCRUM lends it self to refactoring. The iterative nature of SCRUM makes it easy to build a small piece and change and it. But over time that piece will get larger and what if you have a breakthrough after that piece is so large that it will be too difficult to change?Has anyone worked on a project employing domain-driven design? If so, it would be great to get some insight on this one. I'd especially like to hear some success stories, since DDD seems very difficult to get right.Thanks! | Refactoring in domain driven design | design patterns;architecture;object oriented;scrum;domain driven design | I've been a big fan of DDD for a while (with and without the safety net of a test framework). The whole concept and lifecycle of refactoring doesn't change because you're now using a new design methodology. If it will take significant time, it has to have proportional benefit to the project in order to get that time from management. With respect to doing it: in one instance, I partook in a 3 month major refactoring because of a 'breakthrough' in the understanding of the domain model. It required tests to verify the current behaviour, tests to verify the expected behaviour and changes to calling code. The benefits were significant however, and allowed the business to do many more things that it needed to do before but just wasn't able to. In essence, the refactoring was essentially a 'feature'. |
_computergraphics.1479 | Space-filling curves are important in many graphics applications because they help expose spatial locality. We often hear about different algorithms using Z-curves, Morton codes, Hilbert curves, etc. What are the differences between some of these different curves and how do they apply to various applications? | What is the difference between various space-filling curves? | space filling | The difference is how well a mapping preserves locality and how easy it is to encode/decode the keys. The paper Linear Clustering of Objects with Multiple Attributes by H V Jagadish says: Through algebraic analysis, and through computer simulation, we showed that under most circumstances, the Hilbert mapping performed as well as or better than the best of alternative mappings suggested in the literature. On the other hand, z-order is a bit simpler to use, for example compare the various methods listed in Bit Twiddling Hacks for z-order and Wikipedia for Hilbert-order.As for the applications, I think the main advantage in using space filling curves is that they map points from higher dimensional space to space of lower dimension. For example, they make it possible to window query for points using traditional B-tree database index. Again, on the other hand, the disadvantage is that one needs to know the bounds of the input in advance as it is difficult to resize the mapping later.PS: Z-curve is the same as Morton code.PPS: Additional mappings include Peano curve and for applications see also Geohash. |
_unix.64645 | I want to retrieve whatever is between these two tags <tr> </tr> from an html doc. Now I don't have any specific html requirements that would warrant for an html parser. I just plain need something that matches <tr> and </tr> and gets everything in between and there could be multiple trs. I tried awk, which works, but for some reason it ends up giving me duplicates of each row extracted.awk '/<TR/{p=1; s=$0}p && /<\/TR>/{print $0 FS s; s=; p=0}p' htmlfile> newfileHow to go about this? | Text between two tags | shell script;text processing;sed;awk;html | if you only want ... of all <tr>...</tr> do:grep -o '<tr>.*</tr>' HTMLFILE | sed 's/\(<tr>\|<\/tr>\)//g' > NEWFILEfor multiline do:cat HTMLFILE | tr \n | | grep -o '<tr>.*</tr>' | sed 's/\(<tr>\|<\/tr>\)//g' | sed 's/|/\n/g' > NEWFILEcheck the HTMLFILE first of the char | (not usual, but possible) and if it exists, change to one which doesn't exist. |
_unix.263394 | I have a file with multiple tags with a number next to it e.g.<Overall>4other <tags> and data<Overall>2other <tags> and data<Overall>3How would I search through the file and count up all the numbers next to the overall tag? and then divide the number by the number of overall tags, to get an overall average.So for example in the code above the average would be 3.And then loop through all the files in the current directory and list the overall average for each file. | Sum value next to specific pattern | shell script;awk | Using awk (assuming all that is on overall lines is that and a number)awk 'x+=sub(/<Overall>/,){y+=$0}END{print AVG:,y/x}' filex is incremented for every successful sub of <Overall> with nothing. This means that it is only incremented on lines that contain <Overall>.The block after then adds the number that is left on the line to the total.END executes at the end of the program.In the end block the avg is printed.EDIT:for lots of filesawk 'x+=sub(/<Overall>/,){y+=$0}END{print FILENAME,AVG:,y/x}' LISTOFFILES |
_codereview.51765 | I am a big fan of one-liners using sed awk perl and other tools. But there are that are things hard to do in one-liner, such as when you working with a CSV file and there are commas between quotes, or when you want to print a centralized field with printf.A few months ago I wrote ftable more for fun than anything else, but last weekend I took it seriously and created a GitHub repository and a tutorial for it. ftable tutorialftable codeQuestionsDo you know of a tool that's similar to ftable? I hate feeling like re-inventing the wheel.As I am not programmer (I am sysadmin/devops). Is there anybody willing to review the code and spot my endless mistakes?#! /usr/bin/env perl# Author: Tiago Lopo Da Silva# Date: 20/10/2013# Purpose: Print formatted tableuse strict;use warnings;use POSIX;use Switch;use Getopt::Long qw(:config no_ignore_case);use Data::Dumper;our $comma=<comma>;our $dollar=<dollar>;our $pipe=|;our $plus=+;our $minus=-;our $FS=',';our $nb=0;my %h;if ($#ARGV >= 0){my $lf; my $cf; my $rf; my $print;GetOptions( 'l|left:s' => \$lf, 'r|right:s' => \$rf, 'c|center:s' => \$cf, 'p|print:s' => \$print, 'F:s' => \$FS, 'n|noborder' => \$nb, ) || print_usage();%h=get_details($lf,$cf,$rf,$print);}else {%h=get_details();}print_table(\%h);sub get_quoted_fields {# this sub finds quoted fields my $str1 = $_[0]; my $qf; while ( $str1 =~ /(['].*?['])/ ){ $qf.=$1${comma}; $str1 =~ s/$1//; } return $qf;}sub get_translated { my $qf = $_[0]; my $str= $_[1]; my @arr; my %h; if (defined ($qf)) { @arr = split(/$comma/,$qf); } foreach my $i ( @arr ){ my $tmpvar=$i; $i =~ s/$FS/$comma/g; $h{$tmpvar} = $i; } while ( my($key,$value) = each(%h) ){ $key =~ s/\$/\\\$/g; eval \$str =~ s/$key/$value/g; ; } return $str;}sub special_split {#This sub splits strings but taking quoted fields in consideration my $str=$_[0]; $str =~ s/\$/$dollar/g; $str =~ s/\(/<op>/g; $str =~ s/\)/<cp>/g; $str =~ s/\//<slash>/g; my $str1=$str; my $qf; my @a; $qf=get_quoted_fields($str1); my $translated = get_translated($qf,$str); @a = split (/$FS/,$translated); foreach my $i ( @a ){my $safe_fs=$FS;switch($safe_fs) {case '\.' {$safe_fs =~ s/\\//g;}case '\t' {$safe_fs =~ s/\\t/\t/g;}case '\s' {$safe_fs =~ s/\\s/ /g;}} $i =~ s/$comma/$safe_fs/eg; $i =~ s/$dollar/\$/g; $i =~ s/<op>/\(/g; $i =~ s/<cp>/\)/g; $i =~ s/<slash>/\//g; $i =~ s/[']//g; $i =~ s/\s+/ /g; } return @a;}sub fill_str {# This sub fills the string with padding charsmy $f_char=$_[0];my $f_times=$_[1];my $str;$str=$f_charx$f_times;return $str;}sub print_border {# This sub prints horizontal bordermy @length=@{$_[0]};foreach my $i (@length){unless (defined($i)){$i=1;}print $plus;my $counter=0;while ( $counter < ($i+2) ){print $minus;$counter++;}}print $pipe\n;}sub print_left {#This sub prints fields with proper padding in the left side.#It takes two args, 1st length of the maximun field and field content.my $length=$_[0];my $col=$_[1];unless (defined($length)){ $length=;}unless (defined($col)){ $col=;}my $str=printf ' %-.$length.s ','.$col.';;eval $str}sub print_right {#This sub prints fields with proper padding in the right side.#It takes two args, 1st length of the maximun field and field content.my $length=$_[0];my $col=$_[1];unless (defined($length)){ $length=;}unless (defined($col)){ $col=;}my $str=printf ' %.$length.s ','.$col.';;eval $str}sub print_center {#This sub prints fields with proper padding in the both sides.#It takes two args, 1st length of the maximun field and field content.my $length=$_[0];my $col=$_[1];my $str;unless (defined($length)){ $length=1}my $cl=length($col);my $padding=(($length - $cl)/2); my $lp; my $rp;if ( (($length - $cl) % 2 ) == 0 ){$lp=$padding; $rp=$padding; }else{$lp=ceil($padding); $rp=floor($padding); }my $l_str ; my $r_str;$l_str=fill_str( ,$lp);$r_str=fill_str( ,$rp);$str=printf ' %.$length.s ','.$l_str.$col.$r_str.';;eval $str;}sub get_details {# This subs creates a hash containg the whole content of the table, alignment info and# number of columns/ fieldsmy @align = get_align($_[0],$_[1],$_[2]);my @print = get_print($_[3]);my @content;my @tmp_arr;my @tmp_arr2;my @length;my $n_col=0;my $counter=0;my $p_print;if(@print){ $p_print=1; }else{ $p_print=0;}while (<>){@tmp_arr= special_split($_);unless( $p_print ){for ( my $i=0 ; $i <= $#tmp_arr; $i++){$print[$i]=$i; }}my $counter2=0;foreach my $i (@print){$tmp_arr2[$counter2] = $tmp_arr[$i];$counter2++}$counter2=0;foreach my $i (@tmp_arr2){defined($i) && $i =~ s/^\s+//;defined($i) && $i =~ s/\s+$//;$content[$counter][$counter2] = $i;my $li= length($i);if ( defined( $length[$counter2] ) ){if( $li > $length[$counter2] ) {$length[$counter2]=$li;}}else{$length[$counter2]=$li;} $counter2++;}if ( $counter2 > $n_col ){ $n_col=$counter2;}$counter++;}my %details= (content => \@content, # content of the filelength => \@length, # Maximun length of fieldsalign => \@align, # Alignmentn_col => $n_col, # Maximun number of columns/fields);return %details;}sub print_table{my %h = %{$_[0]};my @content=@{$h{content}};my @length=@{$h{length}};my @align=@{$h{align}};my $n_col=$h{n_col};my $counter=0;foreach my $line (@content){$nb || print_border(\@length);my $str;my $counter2=0;for ( my $i=0; $i < $n_col ; $i++ ){my $col = $content[$counter][$i];unless (defined($col)) { $col = }$col =~ s///g;$col =~ s/'//g;my $l=$length[$counter2];$nb || print $pipe;my $left=false; my $right=false;my $center=false;switch ($align[$counter2]){case l { $left=true;}case r { $right=true;}else { $center=true;}}if ( $right eq true ){print_right($l,$col);}if ( $left eq true ){print_left($l,$col);}if ( $center eq true ){print_center($l,$col);}$counter2++;}unless ($nb) {print $pipe\n}else{print \n}$counter++;}$nb || print_border(\@length);}sub get_align {# This sub creates an array with the alignment informationmy $lf = $_[0];my $cf = $_[1];my $rf = $_[2];my @align;defined($lf) && (my @lf = split (/,/,$lf));defined($cf) && (my @cf = split (/,/,$cf));defined($rf) && (my @rf = split (/,/,$rf));foreach my $i (@lf){$align[$i] = l; }foreach my $i (@cf){$align[$i] = c; }foreach my $i (@rf){$align[$i] = r; }shift(@align);return @align;}sub get_print {# This sub creates an array containing the field numbers to be printedmy $print = $_[0];my @print;defined($print) && (my @a = split(/,/,$print));my $counter=1;foreach my $i (@a){$print[$counter] = $i-1;$counter++;}shift(@print);return @print;}sub print_usage {my $usage = << 'EOF';Usage: ftable [OPTIONS] [FILE]Options: -l, --left List of field numbers (separated by comma) to be left aligned -r, --right List of field numbers (separated by comma) to be right aligned -c, --center List of field numbers (separated by comma) to be center aligned It is default if no alignmnet provided -p, --print List of field numbers (separated by comma) to be printed and ordered -n, --noborder Do not print border -F, --field-separator Field separator, if no specified comma (,) is the default valueExamples: ftable -F ':' -p 3,1,6 /etc/passwd ftable -l 1 -c 2,3 -r 4 /tmp/table.csv ftable -n -F ':' /etc/passwdEOFprint $usage;exit 2;} | Command line tools to format tables | perl;csv;formatting | null |
_softwareengineering.319636 | ContextFor my end-of-year project at school I had to create a framework to serve a RESTful JSON API. I wasn't authorized to use a project like Ruby on Rails for instance, Sinatra is allowed since it does not provide any direct way to create a JSON RESTful API. So I decided to use Sinatra as the base of this framework. While my mates are recreating a MVC framework (where the view is JSON) I decided to follow another approach to create this framework. I started from scratch, without any pre-compiled ideas about what philosphy my framework should follow. With this in head I've ended up creating something I called MEA : Models, Envelope, Actions.What I'm asking : I would like to have some reviews about the concept I'm going to descibe. Is it viable ? Is there some stupid ideas in it ?If you have ever created something like a framework to do this kind of JSON-api stuff, can you descibe it.What is MEAGeneral conceptsI've realized the following when I was thinking about how I design a JSON api (it might not be the best practices, though) :Always the same HTTP Routes.Over-using of before_filters etc... (to avoid code-redundancy in Ruby on rails).Using JBuilder to render the view.Keeping this in mind, I've created this way to design a JSON api :HTTP Routes are hard-coded in the framework.Instead of using things like before_filters, a route should be able to call a chain of N methods. => Methods are called actions.It must be easy to describe the chain to the framework (like rails *filters) for a custom dispatching system. => Called MEARoutes.A global read-write context should be passed between every methods called in that chain. => Called Envelope.The models, like in any other frameworks, are a model that represents a database-entity and give a wrapping around this entity to manipulate it in its database.HTTP RoutesIn MEA the HTTP Routes are hard-coded and are described this way :GET /:resource_name(defult sub_call: all)GET /:resource_name/:id(defult sub_call: one)GET /:resource_name/:id/:sub_callPOST /:resource_name => (defult sub_call: create) Excepted body : { sub_call: xx, data: { ... } }PUT /:resource_name/:id => (defult sub_call: update) Excepted body : { sub_call: xx, data: { ... } }DELETE /:resource_name/:id (defult sub_call: delete)DELETE /:resource_name/:id/:sub_callThe sub_call is used to determine the MEARoute that will be used. data holds the raw data (in JSON, like the attributes to change in a model for the put call) of the call.MEARoutes, envelope and actionsMEARoutes are used to decide the chain method that will be called by a sub_call/resource couple call.To make it easily readable, I decided to use YAML, here is a declaration of a chain for a sub_call/resource call :comment_blogpost: - User.check - Blogpost.retrieve - Comment.createUser.check will check the currently logged user and will register it into the envelope.Blogpost.retrieve will get the Blogpost to add the comment on and add this blogpost to the envelope.Comment.create will create the entity representing the comment in the Blogpost.User.check and Blogpost.retrieve are reusable components that are designed to add something into the envelope using the http request. They can stop the chain process by simply returning an HTTP code and some data if needed. A chain MUST, at least, return a code and an empty object in the last action. The returned value will be JSON serialized and returned to the client. Comment.create would call a method to enforce some values in the envelope like : @envelope.must_have :user, :blogpost. If it doesn't have those values, then the chain must stop and return a 500 error since it is the developer role to call the actions correctly.If I want to do something like jbuilder I can create another action that would be getting the needed entities from the envelope and present the data in the way excepted for this API call.The main advantage I see to this pattern is the testability of a simple action.EDIT : Here is a try implementation I've made to test the concept viability GitHub source repository.What do you think about all of this ? All remarks, even negative ones, are welcome ! | Viability of custom framework to serve RESTful API | design patterns;frameworks | null |
_softwareengineering.128840 | We need to do some user documentation for a product we have been working on for the past few sprints. We are now starting a new project in the next sprint and the PO is making the documentation for the product produced previously a User story for this sprint.I am just wondering your opinion on this approach. Personally, I don't agree that documentation is a User Story within Scrum because it doesn't produce any code. EDIT: Thanks for your opinions guys. I had it in the back of my head that a sprint was to implement an increment of working software, but your views have changed my outlook. Thank you for all your answers. | Is documentation a User Story? | scrum;user story | As a user of X, I need to know how X works seems like a legitimate user story to me. This could result in written documentation or online help.The point isn't just code--it's meeting the users' requirements. |
_codereview.108502 | I recently submitted a code sample for a web scraping project and was rejected without feedback as to what they didn't like. The prompt, while I cannot give it here verbatim, basically stated that I needed to write a spider to crawl a site for product items. They suggested using a generic spider to scrape the site in question while using URL rules for efficiency. They gave links to documentation in case you hadn't used scrapy before. I felt like this meant that they didn't mind hiring people unfamiliar with their toolset.Speaking of which we could only use pyquery for dom traversal. I usually would have opted for pure lxml and xpaths.I understood the concept of using rules to limit extraneous requests but after noticing that the site in question contained a sitemap I decided to start there instead.I do know that they explicitly said not to use any outside libraries, so that is why I didn't use Pillow for image processing. However, I did cheat and use requests for some other things that the actual spider didn't utilize but again I wasn't told why my code wasn't good enough. So at this point I would like to learn why.# -*- coding: utf-8 -*-import scrapyfrom scrapy.spiders.sitemap import *from pyquery import PyQuery as pqfrom oxygendemo.items import OxygendemoItemimport oxygendemo.utilitiesfrom oxygendemo.utilities import *class OxygenSpider(SitemapSpider): print 'MY SPIDER, IS ALIVE' name = oxygen allowed_domains = [oxygenboutique.com] sitemap_urls = ['http://www.oxygenboutique.com/sitemap.xml'] sitemap_rules = generate_sitemap_rules() ex_rates = get_exchange_rates() def parse_sitemap_url(self, response): self.logger.info('Entered into parse_sitemap_url method') self.logger.info('Received response from: {}'.format(response.url)) self.logger.debug('Respons status: {}'.format(response.status)) item = OxygendemoItem() d = pq(response.body) parsed_url = urlparse.urlparse(response.url) base_url = get_base(parsed_url) product_info = d('.right div#accordion').children() image_links = d('div#product-images tr td a img') description = product_info.eq(1).text()\ .encode('ascii', 'ignore') item['code'] = str(parsed_url[2].lstrip('/')[:-5]) item['description'] = description item['link'] = parsed_url.geturl() item['name'] = d('.right h2').text() gbp_price = { 'prices': d('.price').children(), 'discount': 0 } item['gbp_price'], item['sale_discount'] = get_price_and_discount( gbp_price ) if 'error' not in self.ex_rates: item['usd_price'] = {0:.2f}.format( item['gbp_price'] * self.ex_rates['USD'] ) item['eur_price'] = {0:.2f}.format( item['gbp_price'] * self.ex_rates['EUR'] ) else: item['usd_price'], item['eur_price'] = ['N/A'] * 2 item['designer'] = d('.right').find('.brand_name a').text() item['stock_status'] = json.dumps(determine_stock_status(d('select') .children())) item['gender'] = 'F' # Oxygen boutique carries Womens's clothing item['image_urls'] = fetch_images(image_links, base_url) item['raw_color'] = get_product_color_from_description(description) yield itemThis is the utilities module I used:# -*- coding: utf-8 -*-import requestsimport jsonimport urlparsefrom pyquery import PyQuery as pqimport redef get_base(parsed_url): base_url = parsed_url[0] + '://' + parsed_url[1] base_url = base_url.encode('ascii', 'ignore') return base_urldef get_exchange_rates(): ''' return dictionary of exchange rates with british pound as base currency ''' url = 'http://api.fixer.io/latest?base=GBP' try: response = requests.get(url) er = json.loads(response.content)['rates'] return er except: return {'error': 'Could not contact server'}def determine_stock_status(sizes): result = {} for i in xrange(1, len(sizes)): option = sizes.eq(i).text() if 'Sold Out' not in option: result[option] = 'In Stock' else: size = option.split(' ')[0] result[size] = 'Sold Out' return resultdef determine_type(short_summary): short_summary = short_summary.upper() S = { 'HEEL', 'SNEAKER', 'SNEAKERS', 'BOOT', 'FLATS', 'WEDGES', 'SANDALS' } J = { 'RING', 'NECKLACE', 'RING', 'BANGLE', 'CHOKER', 'COLLIER', 'BRACELET', 'TATTOO', 'EAR JACKET' } B = { 'BAG', 'PURSE', 'CLUTCH', 'TOTE' } A = { 'PINNI', 'BLOUSE', 'TOP', 'SKIRT', 'KNICKER', 'DRESS', 'DENIM', 'COAT', 'JACKET', 'SWEATER', 'JUMPER', 'SHIRT', 'SKINNY', 'SHORT', 'TEE', 'PANTS', 'JUMPSUIT', 'HIGH NECK', 'GOWN', 'TROUSER', 'ROBE', 'PLAYSUIT', 'CULOTTE', 'JODPHUR', 'PANTALON', 'FLARE', 'CARDIGAN', 'VEST', 'CAMI', 'BEDSHORT', 'PYJAMA', 'BRALET', 'TUNIC', 'HOODY', 'SATEEN', 'BIKER', 'JEAN', 'SWEAT', 'PULL', 'BIKINI', 'LE GRAND GARCON' } types = { 'B': B, 'S': S, 'J': J, 'A': A } for key, val in types.iteritems(): for t in val: if t in short_summary: return key else: return 'R' # Tag as accessory as failsafedef fetch_images(image_links, base_url): ''' base_url will come as unicode change to python string ''' images = [] for image in image_links: images.append(urlparse.urljoin(base_url, image.attrib['src'])) return imagesdef get_price_and_discount(gbp_price): if gbp_price['prices']('.mark').text() == '': # No discount gbp_price['discount'] = '0%' orig_price = float(gbp_price['prices'].parent().text() .encode('ascii', 'ignore')) else: # Calculate discount prices = gbp_price['prices'] orig_price = {0:.2f}.format(float(prices('.mark').text())) new_price = {0:.2f}.format(float(gbp_price['prices'].eq(1).text())) gbp_price['discount'] = {0:.2f}\ .format(float(orig_price) / float(new_price) * 100) + '%' return float(orig_price), gbp_price['discount']def get_raw_image_color(image): ''' Note that Pillow imaging library would be perfect for this task. But external libraries are not allowed via the constraints noted in the instructions. Example: Image.get_color(image) Could be used with Pillow. ''' # only import Pillow image library if this is used # Later from PIL import Image im = Image.open(image) colors = im.getcolors() if colors is None: return None else: return colors[0] # Not functional at this pointdef get_product_color_from_description(description): ''' Will go this route to avoid external imports ''' description = description.upper().split(' ') colors = ( 'BLACK', 'WHITE', 'BLUE', 'YELLOW', 'ORANGE', 'GREY', 'PINK', 'FUSCIA', 'RED', 'GREEN', 'PURPLE', 'INDIGO', 'VIOLET' ) for word in description: for color in colors: if word == color: return color.lower() else: return Nonedef generate_sitemap_rules(): d = pq(requests.get('http://www.oxygenboutique.com').content) # Proof of concept regex can be found here --> http://regexr.com/3c0lc designers = d('ul.tame').children() re_front = r'(http:\/\/)(www\.)(.+\/)((?!' re_back = r').+)' re_middle = 'products|newin|product|lingerie|clothing' for li in designers: ''' This removes 36 requests from the queue ''' link = pq(li.find('a')).attr('href').rstrip('.aspx') re_middle += '|' + link return [(re_front + re_middle.replace('-', r'\-') + re_back, 'parse_sitemap_url')]OxygendemItem() declaration:import scrapyfrom scrapy import Fieldclass OxygendemoItem(scrapy.Item): code = Field() # unique identifier (retailers perspective) description = Field() # Detailed description designer = Field() # manufacturer eur_price = Field() # full (non_discounted) price gender = Field() # F - Female, M - male gbp_price = Field() # full (non_discounted) price image_urls = Field() # list of urls representing the item link = Field() # url of product page name = Field() # short summary of the item raw_color = Field() # best guess of color. Default = None sale_discount = Field() # % discount for sale item where applicable stock_status = Field() # dictionary of sizes to stock status ''' size: quantity Example: { 'L': 'In Stock', 'M': 'In Stock', 'S': 'In Stock', 'XS': 'In Stock' } ''' # 'A' = apparel, 'B' = bags, 'S' = shoes, 'J' = jewelry, 'R' = accessories type = Field() usd_price = Field() # full (non_discounted) price | Scrapy spider for products on a site | python;web scraping;scrapy | Well to start with you have bad practices in your imports. It's recommended to stay away from using from module import * because doing that imports things without explicitly declaring their names. Without realising it, you could be overwriting other functions, including builtins in the module was made carelessly. Instead use just import module or from module import func1, func2, CONST. Especially though, don't do this:import oxygendemo.utilitiesfrom oxygendemo.utilities import *It's totally redundant to have the first line since you're then ignoring it to import everything. In case you don't know, you can still alias plain imports:import oxygendemo.utilities as utilSo you don't even need to worry about the name being too long.Also OxygenSpider is not laid out properly. You have loose code that should probably be in an __init__ function. Let me show you how this works in the interpreter:>>> class A: print Printing class APrinting class ASo what happened there? The print command was run when the class was created. I haven't created any object yet, so what happens when I create an object:>>> A()<__main__.A instance at 0x0000000002CA5588>>>> b = A()>>> Nothing. It's not printing the command that you intended to appear when creating an OxygenSpider object. If you were to wrap it in __init__ though, it would. __init__ is a special function that runs when a new object is created, like so:>>> class A: def __init__(self): print Printing this object>>> A()Printing this object<__main__.A instance at 0x0000000002113488>>>> b = A()Printing this objectYou see now? Nothing happens after the class is created but when actual objects are created __init__ gets run. You should be putting the whole opening block to OxygenSpider in a function like that. Also the variables should be assigned as self.var, and the constants should be in UPPER_SNAKE_CASE and constant lists should be tuples instead. Tuples are made with () and are basically like lists except they cannot be changed.However since you're inheriting from SitemapSpider you also need to run its __init__ function in yours. You need to call it so that your base class is initialised before you run your particular __init__ code. There's a good explanation in this Stack Overflow answerclass OxygenSpider(SitemapSpider): def __init__(self): super(SitemapSpider, self).__init__() print 'MY SPIDER, IS ALIVE' self.NAME = oxygen self.ALLOWED_DOMAINS = (oxygenboutique.com) self.SITEMAP_URLS = ('http://www.oxygenboutique.com/sitemap.xml') self.sitemap_rules = generate_sitemap_rules() self.ex_rates = get_exchange_rates()Also printing when creating an object just to say it's created isn't very nice anyway, you should remove that. |
_webapps.103819 | I want to find out which of my Twitter followed users are most active, or rather most chatty/loud/frequent posters, so that I can reduce the noise in my home feed.I usually just open my feed, see who's filling the current few screenfuls, check who has the highest total tweets score and mute those I don't care about. However the total number doesn't tell much about recent activity, and scanning the home feed is tedious.Is there a more efficient way? | Find the most active Twitter friends | twitter;statistics | null |
_unix.328483 | I found many questions about avoid an app from going to swap,but I need to know a way to make an specific app (chromium) stay as much as possible at swap.Is there any way to do that?Basically whenever it is not focused, it should remain at swap. | how to keep an application, as much/long as possible on the swap? | swap | null |
_unix.232457 | BackgroundI work on a corporate network that is behind a proxy server. I also work with some remote sites that I am able to access via a bastion / jump host ssh proxy.In my ~/.ssh/config I have a proxy configuration for my SSH tunnels that allows the jumping through our bastion hosts in order to reach the remote labsHost *.remoteLab1 ProxyCommand ssh -l USERNAME BASTIONHOST1 nc %h %pHost *.remoteLab2 ProxyCommand ssh -l USERNAME BASTIONHOST2 nc %h %pI use both OSX and Linux so I assume the commands are more or less the sameCurrent SolutionMy current solution is less than ideal. I basically make a socks connection to one of the remote labs such as:ssh -D 1080 remoteLab1ssh -D 1081 remoteLab2Then in both realvnc and chrome I change the proxy server to localhost:1080 / localhost:1081. In chrome I have a plugin that allows me to do this and in VNC its manual.As both of these remote labs have a unique domain I was wondering if there is an easier way playing with routing tables to send all traffic through these socks proxies based on ip addressRequested SolutionGIVEN: A socks5 tunnel is open on port 1080GIVEN: A socks5 tunnel is open on port 1081Requirementsaddresses of domain1.org go through 1080addresses of domain2.org go through 1081fall through case - everything else goes through standard proxy serverNice-to-have'sThe solution is not permanent - it is enabled by a script in conjunction with turning on one of the socks tunnelsIs it possible to also map specific ip addresses as opposed to domains through one of the proxy serversIdeasI'm not really sure at all where to start with all of this. One solution I saw somewhere was to use a proxy.pac however the corporate network already has a proxy.pac and I wasn't sure if there is a way to do a fall-through pac where if not in my custom .pac then use the settings in the corporate .pacUsing the iptables or route command - however both of those are a little out of my knowledge zoneSetting up local loopbacks or something | How to route traffic through different proxy servers based on destination | iptables;proxy;route;socks | null |
_computerscience.4378 | I attempted to implement font rendering using signed distance fields.My program first generates a mono bitmap at font size 64 (using FreeType), then generates an SDF from the bitmap. This is then uploaded into a texture atlas.The results are not very nice and look nothing like the various papers show:My guess is that the bitmap does not have a high enough resolution, butI do not necessarily want to generate SDF's larger than 64px (they have to fit in the atlas). Besides, at 256px, the generated sdf still has artifacts, albeit less noticable unless blown up.So how can I get better results / how am I applying the algorithm wrong? | Signed distance field font looks odd | opengl;signed distance field;font rendering | Hmm, that SDF doesn't look right. It should be much smoother, like this image for instance:(image from this blog).One possible issue I noticed in your description:My program first generates a mono bitmap at font size 64 (using FreeType), then generates an SDF from the bitmap.The initial text needs to be rendered at a much higher resolution than the resulting SDF, so you can get subpixel precision in the distances stored in the SDF. For example, in the original Valve paper, they render the initial mono bitmap at 40964096 in order to generate a 6464 SDF from it. |
_softwareengineering.349963 | I am considering splitting a project from monolithic to server side REST API plus isolated web-based front end (or, also, any other third party consumer) that can be hosted on a distinct server and domain.How should I approach user authentication and authorization? Forms authentication is basically gone, and all calls would be handled the same way to API endpoints, whether they originate from our web app, or a third party app.The server side REST API is going to be the gatekeeper and only allow access conditionally. I would use standard C# ASP.Net membership ideally. Framework would be ASPNetCore with MVC 6. | Authorization and Authentication design for splitting a site into REST API and Web App (AspNetCore MVC) | rest;asp.net mvc;authentication;authorization | First of all, ASP.NET Core doesn't have support for Membership anymore, you would have to use Identity.I recently came across such requirement myself as our applications were growing and, each time, we had to implement membership/identity for each of them.The solution i came up with was to build a centralized authentication server which will accept user credentials, connect to database, authenticate the credentials and generate/return tokens (JWT). This token will serve the purpose of both authentication and authorization through claims. Only this application/server will implement identity.On any client application with protected resources (Authorize), they would have to implement a middleware which will read the token and validate the claims. There is no requirement for the middleware to connect to the database again to validate the claims. This token will be appended to the Authorization header every time a request is made to a protected resource.Every time you create a new application which will use the same authentication server, all you need to do is to implement/inject the validation middleware. There is no need to re-implement identity again.Refer below resources for basics & implementation details.References:https://docs.microsoft.com/en-us/aspnet/core/security/authentication/identityhttps://docs.microsoft.com/en-us/aspnet/core/security/authorization/claimshttps://stormpath.com/blog/token-authentication-asp-net-corehttps://jwt.io/Additional Resources once you are through with the basics:https://stackoverflow.com/questions/18223868/how-to-encrypt-jwt-security-token/44195678#comment75530351_44195678https://stackoverflow.com/questions/44179525/asp-net-core-jwt-bearer-token-custom-validation/44320206#44320206Note: In my scenario, all applications interact with the same database. |
_cstheory.4648 | Suppose we have an orthogonal polygon with holes (all walls are axis-parallel). All vertices can be on integer coordinates, if that helps. Partition the polygon into rectangular rooms. I would like to find the best room to start from, to visit all the rooms (rectangles). There's a limitation on my movement: in any room, I can only leave by two directions, say north and west. (Here best means there would only be one source in the plane dual graph with directed edges showing how to walk from room to room. If more than one source is required, I wish to minimize them.) I have been looking at art gallery problems, and at VLSI papers on building rectilinear floorplans from network flows, and they are all tantalizingly close but far. Can anyone provide suggestions so I can focus my search/proof construction?EDIT to fix problem pointed out by Peter Taylor. I can choose two directions per room. (probably they need to be adjacent, so NE is ok but NS is not.) If I enter one room northward, I am automatically choosing South as one of thst new room's directions. (so only two in or out directions per room) If I choose a direction, and there are multiple rooms adjacent in that direction, I can enter all of them (and all of them then have the reverse direction assigned as one of their two directions), so the naive greedy approach would be to choose the direction that maximizes the number of rooms I can enter at that stage. I hope this is now complete, and understandable. | Find optimal room from which to visit all other rooms in a rectangular floorplan | graph algorithms;cg.comp geom | null |
_unix.44591 | I've been trying to use a SOCKS Proxy which I have been using with success from an Ubuntu 11.4 box with GNOME on my Debian box with KDE.The socks server is bound to the local port 1080 through the following ssh command:ssh -p222 -D 1080 <my_username>@socks_server_domain_nameFollowing the advice I found here: http://emilsedgh.info/blog/index.php?/archives/14-SOCKS-proxy-on-KDE.html I edited my ~/.kde/share/config/kioslaverc file and now it looks like this:jason@debian-laptop:~$ cat ~/.kde/share/config/kioslavercPersistentProxyConnection=true[$Version]socksProxy=socks://localhost:1080update_info=kioslave.upd:kde2.2/r1,kioslave.upd:kde2.2/r2,kioslave.upd:kde2.2/r3However, once I use System Settings->Network Settings->Proxy, I click on Manually specify the proxy settings, but the dialog won't let me hit apply without prompting me to fill in information in the setup dialog:which is not helpful at all, because there is no SOCKS protocol option in the setup dialog. I'd also like to add that, when switching to GNOME in the same box, I am able to run the SOCKS proxy by specifying localhost and 1080 in System->Preferences->Network Proxy, in exact the same way I did it in my Ubuntu box. | SOCKS proxy configuration on KDE 4.4.5 / Debian 6.0.5 | debian;networking;kde;proxy;socks | null |
_unix.287520 | There is a way to prevent rm from deleting mount points?For example, if I have /mnt/backup mounted externally and someone runs rm -rf / I know it will delete the backup contents. My solution is to umount /mnt/backup after the backup concludes. | Behavior of rm - how to prevent deletion of mounted points contents | backup;rm | rm --one-file-system should do the trick. --one-file-system when removing a hierarchy recursively, skip any directory that is on a file system different from that of the corresponding command line argumentSource: http://man7.org/linux/man-pages/man1/rm.1.html |
_vi.7160 | How do I turn vi colors off? I was using vim-tiny on on Ubuntu 14.04. Installed vim-nox. Version is version 7.4.52. Once I installed that, I got all these syntax colors by default. I have my Terminal set to a black background with bright green text. Now when I use vi with the colors, some of the text is unreadable against the dark background. I would rather just turn the colors off. How do I do this? | How do I turn Vi colors off in Ubuntu Linux 14.04 | syntax highlighting;colorscheme;linux;bash | You can use::set t_Co=0This will tell Vim that you're not using a colour terminal. The difference with using :syntax off is that this will still enable some syntax highlighting features with bold, underlined, and reverse video. |
_datascience.17979 | Is there any implementation of scikit-learn function (from sklearn.model_selection import TimeSeriesSplit) under h2o framework?Or what is best practice to implement my custom cross-validation approach inside of h2o? | Time Series cross-validation in h2o | python;scikit learn;cross validation | null |
_softwareengineering.240512 | I work at a mid-sized company (150ish employees, ~10 size engineering team), and most of my projects involve interfacing with lab equipment (oscilloscopes, optical spectrum analyzers, etc) for the purpose of semi-automated test applications. I have run into a few different scenarios where I am unable to efficiently troubleshoot or test new code because I no longer or never had the hardware setup available to me.Example 1: A setup where 10-20 burn-in processes are run independently using a bench top type sensor - I was able to obtain one such sensor for testing and could occasionally steal a second for simulating all of the facets of interfacing to multiple devices (searching, connecting, streaming, etc). Eventually a bug showed up (and ultimately ended up being in the device firmware & drivers) that was very difficult to reproduce accurately with only one unit, but hit near show stopper levels when 10-20 of these devices were in use simultaneously. This is still unsolved and is ongoing.Example 2: A test requiring an expensive optical spectrum analyzer as its core component. The device is pretty old, legacy according to the manufacturer who was acquired by a larger company and basically dissolved, and its only documentation was a long winded (and uninformative) document that seems poorly translated. During initial development I was able to keep the device at my desk, but now its tied up, both physically and in schedule during its 24/7 multi-week tests. When bugs show up related or unrelated to the device, I often need to go through the trouble of testing code external to the application and fitting it in, or writing code blindly and attempting to squeeze in some testing time in between runs, as much of the program logic requires the OSA and the rest of the test hardware to be in place.I guess my question is how should I approach this? I could potentially spend time developing device simulators, but figuring that into the development estimate will balloon it more than most would probably appreciate. It may not accurately reproduce all issues either, and it's pretty rare to see the same equipment used twice around here. I could get better at unit testing...etc...I could also be loud about the issue and make others understand that temporary delays will be required, not much more than a headache for Research and Development but usually a perceived as a joke when pitched to manufacturing. | How to efficiently troubleshoot or test new code when hardware setup to reproduce bugs is difficult or impossible to obtain? | programming practices;testing;hardware;test automation | Management understands it will take longer to develop and maintain software when you don't have full access to test hardware. You need to take this into account when doing your estimates. Part of the acceptance criteria for putting your software into production should be that you have a way to maintain the software under most circumstances without stopping manufacturing. If you're practicing TDD, this should happen pretty much naturally.I used to write software for $60 million aircraft. Obviously, there's a high degree of reliability required, and they are reluctant to give every developer one for their desk. We basically had 5 levels of test environments, with more of the real hardware at each level, up to a full aircraft. I estimate 95% of our software could be developed and debugged only with emulators and unit tests. 95% of the remaining features could be worked on the next level up, and so on.Try to set up similar levels of test environments for yourself. You can't expect to never need access to the real hardware, but if you've set it up so you can't work on your software's GUI without the hardware available, you're wasting valuable time on an expensive resource (not to mention you have some coupling issues with your architecture). Consider that other developers likely have the same issues as you. I would ask the hardware vendor if they already have emulators or other test resources available.You also need to change your mindset somewhat if you only have limited access to hardware. Rather than trying to debug your application in the normal serial manner, you often need to write code specifically for the purpose of gathering information as quickly as possible. For example, perhaps you have a bug and you can think of 10 possible causes. If the only time you can get on a machine is the 15 minutes while the operator is on break, write a Short, Self Contained, Correct (Compilable), Example that triggers the bug and write 10 automated tests using that SSCCE to test your theories and log a bunch of data. Afterward back at your desk you can take as long as you need to sift through the data for your next attempt. The idea is to maximize the utility of your limited time with the hardware. |
_cs.12776 | Let $B=\{b_1=g_1,\cdots,b_n=g_n\}$ be a set of binary variables $b_i$ and their corresponding values $g_i \in \{0,1\}$. Let $M=\{\sum_{e \in A}e \;:\; A \subset B\}$, i.e., $M$ is the set of all possible linear combinations of the equations in $B$.Given $S_i \subset B$ for $i=1,\cdots,m$, is that possible to compute, in polynomial time, a$K \subset M$ with minimum size such that $S_i \cup K$ is a full rank system of equations (i.e., the values of all of the variables can be obtained by solving $S_i \cup K$)?An example: Let $B=\{b_1=1,b_2=0,b_3=1\}$, $S_1=\{b_1=1,b_2=0\}$, and $S_2=\{b_2=0,b_3=1\}$. $K=\{b_1+b_3=0\}$ is the solution because both $S_1\cup K$ and $S_2 \cup K$ can be solved uniquely and $K$ has the minimum size 1. | Is this problem in P: Finding a common key for a collection of systems of equations? | complexity theory;time complexity;np hard;polynomial time;linear algebra | null |
_unix.43819 | I like to work in Linux without using the mouse, because of that I would like to know if there is any method to set a keyboard shortcut to set gnome-terminal tab title. | Keyboard shortcut to set gnome-terminal tab title | linux;keyboard shortcuts;gnome terminal | From Edit -> Keyboard Shortcuts... you can set a shortcut to Set Title. I don't have a default one. |
_unix.219973 | I prefer regular expressions with -regex over the shell pattern syntax of -name. I also want to use the posix-egrep type, so I'd like to do something likealias find=find -regextype posix-egrepbut that is an error since the path has to come before the expression. However, the -regextype has to be first in the expressions (or before using -regex or -iregex).I just want to alias or have a shell function find so that it works the same as usual, just ready to use posix-regex whenever I decide to use the -regex or -iregex option. How can I do this? | How to alias part of expression for find? | find;alias | since the find arguments are positional a function would be a better solution.find(){ command find $1 -regextype posix-egrep ${@:2}}since you want to overwrite the original command you need to use the full path of find so that your new function doesn't create an infinite loop of calling itself.by using a function instead of an alias we can use positional argument variables ($1-$n). since you also might want to add other things to the end of your find we append the command with ${@:2} which appends all but the first argument (your path) using array slicing. |
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