workspace
stringclasses 4
values | channel
stringclasses 4
values | text
stringlengths 1
3.93k
| ts
stringlengths 26
26
| user
stringlengths 2
11
|
|---|---|---|---|---|
clojurians | clojure | Hi, If I want to find the index of the biggest element that is <= 5 , and the index of the biggest element that is <=8, in a sorted array. Can I get the two indices in one search in Clojure? | 2017-11-25T10:11:39.000094 | Tari |
clojurians | clojure | ```
(defn tmp-search
[]
(let [v [1 2 3 4 5 6 7 8 9 10]]
(loop [index1 9
index2 9]
(let [condition1 (<= (get v index1) 5)
condition2 (<= (get v index1) 8)]
(if (and condition1 condition2)
[index1 index2]
(recur
(if condition1 index1 (dec index1))
(if condition2 index2 (dec index2))))))))
``` | 2017-11-25T10:19:27.000033 | Tari |
clojurians | clojure | <@Tari> You could consider a one pass using `reduce-kv`
```
(reduce-kv (fn [[ndx1 ndx2] k v]
(cond-> [ndx1 ndx2]
(<= v 5) (assoc 0 k)
(<= v 8) (assoc 1 k)))
[nil nil]
[1 2 3 4 5 6 7 8 9 10])
``` | 2017-11-25T11:03:48.000030 | Dirk |
clojurians | clojure | I suppose your approach is more efficient <@Tari> in that it traverses a part of the sequence from the end. You could force that into a single-pass `reduce` by using `reduced` to stop things. Thinking something like:
```
(take 2
(reduce (fn [[ndx1 ndx2 ndx :as acc] v]
(if (and ndx1 ndx2)
(reduced acc)
(cond-> [ndx1 ndx2 (dec ndx)]
(and (nil? ndx1) (<= v 5)) (assoc 0 ndx)
(and (nil? ndx2) (<= v 8)) (assoc 1 ndx))))
[nil nil 9]
(rseq [1 2 3 4 5 6 7 8 9 10])))
``` | 2017-11-25T12:15:29.000011 | Dirk |
clojurians | clojure | Would you recommend using <https://github.com/funcool/cats> on a project, or are there better FP librairies out there? (for simple functor/monad stuff) | 2017-11-25T13:09:05.000003 | Lucio |
clojurians | clojure | Actually, my only real use-case right now is using Either to model failure instead of throwing exceptions | 2017-11-25T13:10:04.000123 | Lucio |
clojurians | clojure | Have you also seen <https://clojure.github.io/algo.monads/> <@Lucio>? | 2017-11-25T13:33:09.000080 | Cherelle |
clojurians | clojure | I've only heard good things about it. I know that <@Shameka> is a fan | 2017-11-25T13:45:28.000123 | Evan |
clojurians | clojure | cats is ok <@Lucio> - it was the best of the clojure fp libs i tried. the context stuff is a bit awkward, and i end up writing sugar macros for `(with context ... (mlet [...` | 2017-11-25T14:38:38.000104 | Shameka |
clojurians | clojure | they took out the monad transformer stuff - i had to resurrect it for one of my libs (uses a promise-state transformer) | 2017-11-25T14:40:00.000106 | Shameka |
clojurians | clojure | and there is no reader or continuation or comonad stuff | 2017-11-25T14:42:57.000028 | Shameka |
clojurians | clojure | but what is there is solid and straightforward - i’ve come across only a couple of bugs in 2 years of heavy use in both clj and cljs | 2017-11-25T14:44:49.000019 | Shameka |
clojurians | clojure | and if you use `either` to model failure you might also want to take a look at <https://github.com/zalando-stups/cats.match> | 2017-11-25T14:51:58.000074 | Shameka |
clojurians | clojure | Since these sorts of solutions slow the code down, I’ve never used the either in production. But what’s the driver to avoid the exceptions? | 2017-11-25T14:52:33.000045 | Sandy |
clojurians | clojure | <@Sandy> I just thought it would be a neater way to differentiate between "expected" failure-like return values and actual exceptions | 2017-11-25T15:42:14.000123 | Lucio |
clojurians | clojure | for example, I am implementing a unification algorithm. When unification fails it's not really an error, just a failure scenario that the caller will handle | 2017-11-25T15:42:45.000065 | Lucio |
clojurians | clojure | a try/catch seemed a bit odd in that case | 2017-11-25T15:42:52.000014 | Lucio |
clojurians | clojure | I could return a custom map with a success/failure tag, but in that case why not use functors and get chaining etc for free... | 2017-11-25T15:43:12.000066 | Lucio |
clojurians | clojure | Well one reason is that they are opaque. That’s my biggest criticism against using functions instead of data, there are few ways to introspect them. | 2017-11-25T15:48:01.000029 | Sandy |
clojurians | clojure | But either way the chaining isn’t free, since either method requires using non standard Clojure forms instead of let, do, etc | 2017-11-25T15:48:47.000027 | Sandy |
clojurians | clojure | But I agree exceptions are not the answer for this. | 2017-11-25T15:49:07.000004 | Sandy |
clojurians | clojure | <@Sandy> ah yes you are right, I was using the term "free" a bit too freely. I am open to better approaches! | 2017-11-25T16:00:18.000089 | Lucio |
clojurians | clojure | is there a way to tell `(for [[k v] someMap] ...)` to process the elements in order sorted by 'k' ? | 2017-11-25T16:37:24.000057 | Berry |
clojurians | clojure | <@Berry> `(for [[k v] (sort-by key someMap)] ...)` | 2017-11-25T16:38:15.000054 | Margaret |
clojurians | clojure | and, incidentally `(sort someMap)` will return key/value pairs in the same order as `(sort-by key someMap)` - when sorting collections it sorts by the size, then first item, then second item if first items sort equal | 2017-11-25T16:40:29.000105 | Margaret |
clojurians | clojure | I guess technically sort-by key might be different if sort thought two of your keys were equal even though hash does not | 2017-11-25T16:41:13.000048 | Margaret |
clojurians | clojure | fun ```+user=> (assoc {} [:a] 0 '(:a) 1)
{[:a] 1}
``` | 2017-11-25T16:42:00.000068 | Margaret |
clojurians | clojure | Is there a way to filter a collection with various rules? Fox example:
```(def jobs [{:id "f26e890b-df8e-422e-a39c-7762aa0bac36",
:type "type1",
:urgent false}
{:id "ed0e23ef-6c2b-430c-9b90-cd4f1ff74c88",
:type "type2",
:urgent true}
{:id "690de6bc-163c-4345-bf6f-25dd0c58e864",
:type "type3",
:urgent false}
{:id "c0033410-981c-428a-954a-35dec05ef1d2",
:type "type2",
:urgent false}])```
I want to get the jobs with type 2, but considering this: return only urgent jobs if they exists. If not, return jobs with the same type that are not urgent. Just to avoid using lots of ifs… is there a way to do this with `filter`? | 2017-11-25T16:45:40.000030 | Audie |
clojurians | clojure | <@Audie> `(or (seq (filter :urgent jobs)) ...)` | 2017-11-25T16:47:37.000100 | Margaret |
clojurians | clojure | oh, the type 2 part | 2017-11-25T16:47:58.000018 | Margaret |
clojurians | clojure | `(let [type2 (filter (comp #{"type2"} :type) jobs)] (or (seq (filter :urgent type2)) type2))` | 2017-11-25T16:49:21.000093 | Margaret |
clojurians | clojure | <@Margaret>
in this case `type2` will have all the jobs right?
Do I have to put the `urgent` part inside the `let` somehow? | 2017-11-25T17:01:19.000054 | Audie |
clojurians | clojure | type2 will have all the type2 jobs, `(or (seq (filter ....)) ...)` ensures that you look at the regular jobs if none of them are urgent | 2017-11-25T17:02:10.000114 | Margaret |
clojurians | clojure | but otherwise you get the urgent ones only | 2017-11-25T17:02:18.000068 | Margaret |
clojurians | clojure | I tried in my application and it works perfectly! thanks | 2017-11-25T17:09:31.000032 | Audie |
clojurians | clojure | What is wrong with this macro?
```
;; (comment [1;31mjava.lang.ClassCastException[m: [3mclojure.lang.Symbol cannot be cast to clojure.lang.Keyword[m)
```
so the two 'small' examples work fine, but when I merge the maps, I get an error | 2017-11-25T17:19:51.000004 | Berry |
clojurians | clojure | ```
(defmacro def-fsi [args]
`(do
~@(for [[v ks] (sort-by key args)
k ks]
`(clojure.spec.alpha/def ~k ~v))))
(macroexpand-1
'(def-fsi {number? [::a]}))
#_ (comment
(do (clojure.spec.alpha/def :a.aa-util/a number?)))
(macroexpand-1
`(def-fsi {::foo [::cat]}))
#_ (comment
(do (clojure.spec.alpha/def :a.aa-util/cat :a.aa-util/foo)))
(macroexpand-1
'(def-fsi
{number [::a]
::foo [::cat]}))
Unandled java.lang.ClassCastException
clojure.lang.Symbol cannot be cast to clojure.lang.Keyword
``` | 2017-11-25T17:20:08.000064 | Berry |
clojurians | clojure | <@Berry> is it `number` that it doesn't like? | 2017-11-25T17:21:28.000063 | Margaret |
clojurians | clojure | good cll; unfortunately
```
(macroexpand-1
'(def-fsi
{number? [::a]
::foo [::cat]}))
```
also give same error | 2017-11-25T17:22:04.000004 | Berry |
clojurians | clojure | number? is also a symbol rather than a keyword | 2017-11-25T17:22:26.000056 | Margaret |
clojurians | clojure | what I don't get is why does
```
;; works
(macroexpand-1
'(def-fsi {number? [::a]}))
``` | 2017-11-25T17:22:31.000023 | Berry |
clojurians | clojure | oh | 2017-11-25T17:22:37.000060 | Margaret |
clojurians | clojure | `{number? [::a]}` and `{::foo [::cat]}` works, but when I merge the two maps -- BAM, error -- can't even macro expand | 2017-11-25T17:23:16.000012 | Berry |
clojurians | clojure | `(sort-by key {'a 20 :fo 30})` -- totally your fault for suggesting (sort-by key ...) :slightly_smiling_face: | 2017-11-25T17:25:38.000012 | Berry |
clojurians | clojure | so clojure's sort can't compare keyword vs symbol | 2017-11-25T17:25:50.000068 | Berry |
clojurians | clojure | you could provide a compare that knows how to | 2017-11-25T17:26:12.000109 | Margaret |
clojurians | clojure | I actualy doh't care about the order so long as it's deterministic | 2017-11-25T17:26:38.000068 | Berry |
clojurians | clojure | maybe I'll just cast everything t strings | 2017-11-25T17:26:43.000035 | Berry |
clojurians | clojure | <@Berry> `(fn [coll] (into [(type (first coll))] coll))` - that ensures that every item in the collection has an item of type Class as its first element | 2017-11-25T17:27:40.000064 | Margaret |
clojurians | clojure | and the second elements would only be compared if the types of their first elements were the same, etc. | 2017-11-25T17:27:57.000009 | Margaret |
clojurians | clojure | does that get around this issue here: (sort [[:foo] ["hello"]]) ? | 2017-11-25T17:30:27.000005 | Berry |
clojurians | clojure | hmm... it's not working as I expected... | 2017-11-25T17:40:14.000006 | Margaret |
clojurians | clojure | <@Berry> ```+user=> (defn weird-compare [x y] (if (= (type x) (type y)) (compare x y) (compare (str (class x)) (str (class y)))))
#'user/weird-compare
+user=> (weird-compare :a :b)
-1
+user=> (weird-compare :a "b")
-7
+user=> (sort weird-compare [:a "b" 'c 3])
(:a c 3 "b")
+user=> (sort weird-compare [:a "b" 'c 3 66 2 50])
(:a c 2 3 50 66 "b")
``` | 2017-11-25T17:48:55.000023 | Margaret |
clojurians | clojure | its order is stable, and you get arbitrary order if they are not equal | 2017-11-25T17:49:13.000095 | Margaret |
clojurians | clojure | it's not quite right yet for k/v or collections yet | 2017-11-25T17:49:26.000043 | Margaret |
clojurians | clojure | If you search for 'cc-cmp' on this page, you can find a function I wrote a couple years back that tries to be a 'universal comparator' between objects of different classes, sorting first by class names alphabetically, then by class-specific means between objects of the same class: <https://github.com/jafingerhut/thalia/blob/master/doc/other-topics/comparators.md> | 2017-11-25T18:31:28.000060 | Micha |
clojurians | clojure | It doesn't succeed at being universal, quite, but it goes a lot farther than clojure.core/compare does. | 2017-11-25T18:31:50.000009 | Micha |
clojurians | clojure | Isn’t that just map, or perhaps the result of (map f)? | 2017-11-25T19:49:24.000026 | Sandy |
clojurians | clojure | I'm using timbre for logging and wondering if there's any way how to change the log level of running application from outside.
Sometimes, I want to raise the logging level temporarily - mostly for staging/production environment.
I was thinking about something like jmx... | 2017-11-25T19:52:29.000028 | Terra |
clojurians | clojure | set-level! just changes a key in an atom, but you could easily hook up an api to alter it. My app starts a localhost only socket server that we sometimes connect to in order to change the log level, or the logged namespaces | 2017-11-25T19:54:12.000048 | Margaret |
clojurians | clojure | I was thinking about socket repl but not sure if that's feasible in terms of security compliance on production :slightly_smiling_face:.
Nevertheless, thanks for advice. Maybe I'll try to add simple jmx api | 2017-11-25T20:02:59.000023 | Terra |
clojurians | clojure | it's localhost only by default | 2017-11-25T20:03:31.000041 | Margaret |
clojurians | clojure | if they are on localhost, there's nothing they could do via the socket that they couldn't do easier with a shell | 2017-11-25T20:03:49.000007 | Margaret |
clojurians | clojure | That sounds reasonable. Will speak to ops guy and see if that's feasible.
Thanks! | 2017-11-25T20:04:27.000034 | Terra |
clojurians | clojure | @jumar you don’t actually need the full repl - the socket server can be used to trigger the invocation of an arbitrary function with args | 2017-11-25T20:47:32.000004 | Sonny |
clojurians | clojure | <https://clojure.org/reference/repl_and_main> | 2017-11-25T20:49:10.000033 | Sonny |
clojurians | clojure | I keep forgetting it can do that, that's smart | 2017-11-25T20:58:22.000002 | Margaret |
clojurians | clojure | spec is not behaving the way I expec it to
is there a way to query the "spec database" to see what is "registered" corresponding to a given keyword/spec ? | 2017-11-26T05:11:11.000071 | Berry |
clojurians | clojure | Yep, there’s a private atom & a helper which derefs and returns the current value. | 2017-11-26T05:54:17.000006 | Wendi |
clojurians | clojure | Can you point me at the documentation of the helper function? don'ts see it in the spec guide. | 2017-11-26T06:01:23.000059 | Berry |
clojurians | clojure | there is (defn get-spec
“Returns spec registered for keyword/symbol/var k, or nil.”
[k]
(get (registry) (if (keyword? k) k (->sym k)))) from the source | 2017-11-26T06:34:08.000003 | Daine |
clojurians | clojure | What are the benefits of using `keyword` over `string`? In particular, in a map? | 2017-11-26T07:31:15.000014 | Mina |
clojurians | clojure | ```
(:foo {:foo 20})
("hello" {"hello" 20})
```
kw works, string gives error | 2017-11-26T07:55:21.000040 | Berry |
clojurians | clojure | <@Mina> there's a performance benefit - because of interning, Clojure Keywords are very fast to check for equality (essentially a pointer comparison), making for fast lookups in maps; they also then to consume less memory. There's also a practical benefit that keywords are functions of the maps that (potentially) contain them as keys. Finally, IMO, there's a clarity benefit: when you see a piece of data as a keywork, you know that it's a programmatic name, not content meant to be shown to a user; Strings have that ambiguity. | 2017-11-26T07:56:00.000013 | Danyel |
clojurians | clojure | <@Berry>: keyword implement IFn and act as functions, strings don't. Similarly, you can't use a number as a function like `(1 ["foo" "bar" "baz"])`. However, maps implement IFn, so you can do `({"hello" 20} "hello")`. | 2017-11-26T08:50:09.000070 | Basil |
clojurians | clojure | ok thanks.
One more question, do you use keywords scattered in your codebase or abstract them using a `def`?
What I mean:
```
(def name :name)
(name {:name "itaied"})
```
Rather than
`(:name {:name "itaied"})` | 2017-11-26T08:55:50.000047 | Mina |
clojurians | clojure | so that if the model name changes (lets say that the map is a dynamic variable), you have to change it in only one place | 2017-11-26T08:56:48.000058 | Mina |
clojurians | clojure | like `:name` change to `:fullname` | 2017-11-26T08:57:02.000057 | Mina |
clojurians | clojure | This is something I've also been interested in, and has been one of the things I've felt myself wanting monads for. | 2017-11-26T09:06:53.000001 | Jodie |
clojurians | clojure | <@Jodie> have you ended up using this approach on any project? | 2017-11-26T09:46:15.000085 | Lucio |
clojurians | clojure | <@Mina> I know why you may feel this is a good idea, but from experience, I recommend using keywords in their literal form, not abstracted behind a name. | 2017-11-26T09:49:32.000089 | Danyel |
clojurians | clojure | This level of indirection is unlikely to make your change non-breaking, because the keyword will probably end up being exposed raw somewhere, e.g serialized over the network | 2017-11-26T09:51:09.000064 | Danyel |
clojurians | clojure | but then the change would be in one place, doesn't it? | 2017-11-26T10:16:31.000008 | Mina |
clojurians | clojure | Hey folks. I’m trying to parse a string of the format `aaa bbb "ccc" {:a 1} foo bar...`, where non-bracketed whitespace-separated parts are to be read verbatim, and `{..}`, `#{..}` and `[..]`-parts are to be read as ClojureScript expressions. What’s the easiest way to do the expression read? I had a look at `clojure.edn/read-string`, but it does not return the unread tail, and I wouldn’t want to count brackets manually. | 2017-11-26T11:27:31.000066 | Maryann |
clojurians | clojure | <@Mina> No, it will be everywhere: instead of changing a keyword throughout the code you’ll need to change a variable throughout the code. If you don’t, you’ll end up with moral equivalent of `(def fourteen 17)`. | 2017-11-26T11:40:55.000024 | Maryann |
clojurians | clojure | that reminds me of this lib <https://github.com/gfredericks/seventy-one> | 2017-11-26T11:42:22.000059 | Margaret |
clojurians | clojure | Not yet, no. | 2017-11-26T11:57:57.000091 | Jodie |
clojurians | clojure | <@Mina> it's not considered idiomatic clojure, people simply use keywords and repeat them whenever they need to, you should also know that there's another feature regarding Clojure keywords that is useful to provide this isolation you're looking for, it's called namespaced keywords. Check this article for more info on that: <https://kotka.de/blog/2010/05/Did_you_know_III.html> | 2017-11-26T12:18:31.000081 | Ahmad |
clojurians | clojure | also, if you define a name for your keywords you would have to require them in the other namespaces to use them, therefore, keywords and namespaced keywords are easier to use. | 2017-11-26T12:21:51.000060 | Ahmad |
clojurians | clojure | ( for extremely large values of fourteen ) | 2017-11-26T12:29:29.000084 | Magda |
clojurians | clojure | is there a nice way to interface Clojure with either Rust, C, or C++ ?
my ideal setup would be:
1. Clojure has a DSL for Rust/C/C++
2. I write some high performance code in this DSL
3. at runtime, this DSL -> Rust/C/C++ -> *.so -> dynamic loads as JNI -> I can call it from Clojure
The only structured I need to pass back & forth is float-array, int-array, and double-array | 2017-11-26T15:41:49.000021 | Berry |
clojurians | clojure | i’ve used jna for integration with `C` | 2017-11-26T15:48:44.000019 | Jonas |
clojurians | clojure | and it was pretty enjoyable | 2017-11-26T15:48:48.000090 | Jonas |
clojurians | clojure | <https://github.com/Chouser/clojure-jna/> | 2017-11-26T15:49:10.000035 | Jonas |
clojurians | clojure | it seems like rust supports being called like a c function, <https://doc.rust-lang.org/book/first-edition/ffi.html#calling-rust-code-from-c> | 2017-11-26T15:56:38.000009 | Jonas |
clojurians | clojure | so it seems like you could setup rust code to be called from clojure-jna, although it might involve some boilerplate | 2017-11-26T15:57:07.000023 | Jonas |
clojurians | clojure | the same will apply for c++, where you would create c wrapper functions to your c++ code | 2017-11-26T15:57:25.000037 | Jonas |
clojurians | clojure | I've used Clojure with JNI directly, it was straightforward to follow the JNI docs. You have to be a little careful to make sure pointers passed to native code don't get garbage-collected. I think there is some overhead involved in the interaction between native code and JVM, which might matter if there is a lot of calling back-and-forth between the native code and JVM code. | 2017-11-26T17:06:24.000102 | Edwin |
clojurians | clojure | I currently have a boot process that looks like:
```
(deftask learning-dev []
(comp
(repl :port 4001)
(watch)
(fn [next]
(fn [fileset]
(require 'server.ss-web :reload)))))
```
the goal is to auto reload all *.clj *.cljc files
unfortuantely, it's not doing that; how can I fix this? | 2017-11-26T17:13:00.000052 | Berry |
clojurians | clojure | (server.ss-web) is a ns that happens to require all the namespaces I care about | 2017-11-26T17:13:12.000036 | Berry |
Subsets and Splits
No saved queries yet
Save your SQL queries to embed, download, and access them later. Queries will appear here once saved.