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clojurians | clojure | and ```clojure.core/namespace
([x])
Returns the namespace String of a symbol or keyword, or nil if not present.``` | 2017-12-06T16:37:37.000059 | Daniell |
clojurians | clojure | They are consistent about what they called "name" and what they call "namespace". | 2017-12-06T16:37:58.000404 | Daniell |
clojurians | clojure | If I `partition` over a sequence, and the 'n' I'm using is larger than the size of the sequence, partition returns an empty list.
```
(partition 100 (range 10)) => ()
```
I can see how that's important if you're expecting your groups to be a fixed size, but is there a similar function that returns any remainders? | 2017-12-06T17:00:51.000708 | Kristan |
clojurians | clojure | I wanted the return to be:
```
((0 1 2 3 4 5 6 7 8 9))
``` | 2017-12-06T17:01:11.000355 | Kristan |
clojurians | clojure | Ah, there's actually a comment from Rich Hickey on this: <https://groups.google.com/forum/#!msg/clojure/ZK0zRhAjeJ8/4sM2tDz4_iAJ>
"The current logic pushes the onus on the producer of the data, where it
belongs, rather then the consumer."
I'll go with that. | 2017-12-06T17:06:35.000402 | Kristan |
clojurians | clojure | see `partition-all` | 2017-12-06T17:07:19.000069 | Guillermo |
clojurians | clojure | there are other arguments to `partition` that can help, too. | 2017-12-06T17:07:41.000079 | Guillermo |
clojurians | clojure | <@Kristan> you can get the behavior you want by providing an empty padding collection. You need to specify a step size to satisfy the arity, so it'd be `(partition 100 100 [] (range 10))` | 2017-12-06T17:15:19.000380 | Lavenia |
clojurians | clojure | Is there an idiomatic/performant way to select a random element from a hash-set? (rand-nth (seq set-value)) doesn't feel right. | 2017-12-06T17:15:55.000526 | Wilda |
clojurians | clojure | Hi all. I want to write function to get data with `(require '[korma.core :as kc])`.
```(defn get-message*
([query] (kc/select message (kc/where query)))
([query & fields] (kc/select message (kc/where query) (apply kc/fields fields))))```
It looks ok, but. select is a macro and it want to use it like this:
```(kc/select message (kc/where query) (kc/fields field1 field2))```
And as result it breaks here: `(apply kc/fields fields)`.
How to deal with this? | 2017-12-06T17:18:07.000246 | Marcos |
clojurians | clojure | to generate a call to a macro, you usually need to create another macro | 2017-12-06T17:19:01.000274 | Margaret |
clojurians | clojure | Yeah, I thought about macro-apply. Is there one? I dunno how to write it | 2017-12-06T17:19:27.000059 | Marcos |
clojurians | clojure | ```
`(kc/select ~message (kc/where ~query) (kc/fields ~@fields))
``` | 2017-12-06T17:19:53.000138 | Margaret |
clojurians | clojure | ah | 2017-12-06T17:19:59.000380 | Marcos |
clojurians | clojure | no, but there is ~@ | 2017-12-06T17:20:00.000258 | Margaret |
clojurians | clojure | Yeah, I forgot about ~@. | 2017-12-06T17:20:13.000263 | Marcos |
clojurians | clojure | Cool! Thanks, <@Margaret> | 2017-12-06T17:20:24.000002 | Marcos |
clojurians | clojure | just remember that to do a multi-arity macro you need to make a macro that expands to another call to the macro | 2017-12-06T17:20:46.000210 | Margaret |
clojurians | clojure | you can’t just call it the normal way | 2017-12-06T17:20:51.000082 | Margaret |
clojurians | clojure | Okay, thanks | 2017-12-06T17:21:06.000653 | Marcos |
clojurians | clojure | oh, looking again, I probably did `message` wrong there | 2017-12-06T17:21:58.000435 | Margaret |
clojurians | clojure | Yeah, I noticed | 2017-12-06T17:22:14.000072 | Marcos |
clojurians | clojure | Also. How I should to eval this? Call eval? | 2017-12-06T17:22:28.000158 | Marcos |
clojurians | clojure | oh - right - to do this with runtime generated data… | 2017-12-06T17:22:51.000240 | Margaret |
clojurians | clojure | ```(defn get-message*
([query] (kc/select message (kc/where query)))
([query & fields] (eval `(kc/select message (kc/where ~query) (kc/fields ~@fields)))))
``` | 2017-12-06T17:23:30.000012 | Marcos |
clojurians | clojure | ideally you can find a version of this that doesn’t require macros on runtime generated collections, but if that’s the best option all things considered yeah you end up with eval | 2017-12-06T17:23:38.000431 | Margaret |
clojurians | clojure | I also can create raw sql query without macros.. Ill think about this later | 2017-12-06T17:24:20.000283 | Marcos |
clojurians | clojure | Is there an idiomatic/performant way to select a random element from a hash-set? (rand-nth (seq set-value)) doesn't seem to perform very well. It is about the same as shuffling a seq and taking the first element. | 2017-12-06T17:36:13.000444 | Wilda |
clojurians | clojure | It feels like there should be a much faster way of doing this. | 2017-12-06T17:38:08.000040 | Wilda |
clojurians | clojure | <@Marcos> Another option is to stop using Korma (it's no longer maintained, is it?) and use HoneySQL instead with `clojure.java.jdbc` -- HoneySQL is designed to let you compose query fragments together. | 2017-12-06T17:42:56.000320 | Daniell |
clojurians | clojure | <@Wilda> a hash set doesn't implement anything with an O(1) access guarantee, just O(n), so I don't think there's anyway to access those elements except sequentially... | 2017-12-06T17:45:29.000363 | Daniell |
clojurians | clojure | I see, thanks! | 2017-12-06T17:46:34.000558 | Wilda |
clojurians | clojure | <@Daniell>, I like korma for table relationship definitions and as result some features like "with". Is there something like korma what is still maintaining ? | 2017-12-06T17:52:17.000233 | Marcos |
clojurians | clojure | <@Marcos> I think that whole entity-relationship thing kinda flies in the face of Clojure's raw data approach... I suspect there are ORM-like alternatives to Korma but I doubt any of them are well-maintained: it's just not really idiomatic (IMO). | 2017-12-06T17:54:05.000134 | Daniell |
clojurians | clojure | hm.. Okay. <@Daniell>, honeySQL only library what I should consider to use? | 2017-12-06T17:55:06.000135 | Marcos |
clojurians | clojure | <https://github.com/jkk/honeysql> | 2017-12-06T18:00:06.000584 | Daniell |
clojurians | clojure | (and then `org.clojure/java.jdbc` for executing the queries -- which you're almost certainly already using under the hood via Korma) | 2017-12-06T18:00:53.000008 | Daniell |
clojurians | clojure | yeah, I use jdbc in korma. Very old version of jdbc (0.3.7 instead of last 0.7.3) | 2017-12-06T18:02:22.000257 | Marcos |
clojurians | clojure | Lots of changes since then -- another reason to avoid Korma! | 2017-12-06T18:02:47.000426 | Daniell |
clojurians | clojure | 0.7.3 brings reducible queries, for example! | 2017-12-06T18:03:21.000241 | Daniell |
clojurians | clojure | uhh, I already want to switch to HoneySQL | 2017-12-06T18:03:42.000268 | Marcos |
clojurians | clojure | Okay. Another question, It is still related to korma | 2017-12-06T18:03:59.000083 | Marcos |
clojurians | clojure | ```$ psql testdb
testdb=> \d message
Table "public.message"
Column | Type | Collation | Nullable | Default
-----------------+--------------------------+-----------+----------+-------------------------------------
/* snipped */
time_sent | timestamp with time zone | | not null |
/* snipped */
$ lein repl
project.scratch=> (require '[korma.core :as kc]
#_=> '[clj-time.core :as t]
#_=> '[clj-time.coerce :as tc])
nil
project.scratch=> (let [timestamp (tc/to-sql-date (t/now))
#_=> msg {:time_sent timestamp, /* snipped */}]
#_=> (println "Trying to insert: " (:time_sent msg))
#_=> (println "What is inserted: " (:time_sent (kc/insert message (kc/values msg)))))
Trying to insert: #inst "2017-12-06T22:43:58.074-00:00"
What is inserted: #inst "2017-12-06T22:00:00.000000000-00:00"
nil``` | 2017-12-06T18:04:07.000523 | Marcos |
clojurians | clojure | Im using postgresql.
Im trying to insert timestamp into table, but I get time without minutes and seconds. Why? | 2017-12-06T18:05:27.000231 | Marcos |
clojurians | clojure | Could it be Korma? | 2017-12-06T18:05:33.000478 | Marcos |
clojurians | clojure | I am immediately suspicious of /* snipped */ | 2017-12-06T18:07:50.000237 | Rebeca |
clojurians | clojure | Okay, Ill return snipped now | 2017-12-06T18:08:21.000164 | Marcos |
clojurians | clojure | I suspect because you're converting it to a SQL Date rather than a timestamp and the JDBC conversion strips the time portion (modulo the TZ adjustment) | 2017-12-06T18:08:31.000317 | Daniell |
clojurians | clojure | or where the timestamp is being generated and written | 2017-12-06T18:08:35.000035 | Rebeca |
clojurians | clojure | <@Rebeca> Timestamp generating in let. | 2017-12-06T18:09:14.000194 | Marcos |
clojurians | clojure | yeah, but where is it written to the database? | 2017-12-06T18:09:31.000293 | Rebeca |
clojurians | clojure | <@Rebeca> last println | 2017-12-06T18:10:01.000085 | Marcos |
clojurians | clojure | `(kc/insert ...` | 2017-12-06T18:10:09.000229 | Marcos |
clojurians | clojure | and what does kv/values return? | 2017-12-06T18:10:40.000345 | Rebeca |
clojurians | clojure | kc | 2017-12-06T18:10:43.000106 | Rebeca |
clojurians | clojure | Hm, ill chek it now | 2017-12-06T18:10:54.000518 | Marcos |
clojurians | clojure | <@Rebeca>
```project.scratch=> (kc/values message {:account_id 3, :dest_account_id 4, :time_sent (tc/to-sql-date (t/now)), :content "hello"})
{:table "message", :name "message", :pk :id, :db nil, :transforms (), :prepares (), :fields [], :rel {"account" #object[clojure.lang.Delay 0x47aa5b5b {:status :pending, :val nil}], "chat" #object[clojure.lang.Delay 0x2b69f1d1 {:status :pending, :val nil}]}, :values [{:account_id 3, :dest_account_id 4, :time_sent #inst "2017-12-06T23:11:24.302-00:00", :content "hello"}]}``` | 2017-12-06T18:11:56.000121 | Marcos |
clojurians | clojure | It contains not stripped time | 2017-12-06T18:12:12.000425 | Marcos |
clojurians | clojure | <@Daniell>, how can I check this? | 2017-12-06T18:13:04.000172 | Marcos |
clojurians | clojure | <https://github.com/clj-time/clj-time/blob/master/src/clj_time/coerce.clj#L54> | 2017-12-06T18:14:14.000340 | Rebeca |
clojurians | clojure | <@Daniell> is right of course | 2017-12-06T18:14:24.000362 | Rebeca |
clojurians | clojure | <https://github.com/clj-time/clj-time/blob/master/src/clj_time/coerce.clj#L85-L89> | 2017-12-06T18:14:48.000241 | Rebeca |
clojurians | clojure | FWIW <@Marcos> We use `tc/to-date` rather than `tc/to-sql-date` in our code. | 2017-12-06T18:14:55.000153 | Daniell |
clojurians | clojure | <https://docs.oracle.com/javase/7/docs/api/java/sql/Date.html> | 2017-12-06T18:15:16.000536 | Rebeca |
clojurians | clojure | <@Daniell> with to-date it throws an error
```project.scratch=> (kc/insert message (kc/values {:account_id 3, :dest_account_id 4, :time_sent (tc/to-date (t/now)), :content "hello"}))```
`PSQLException Can't infer the SQL type to use for an instance of java.util.Date. Use setObject() with an explicit Types value to specify the type to use. org.postgresql.jdbc2.AbstractJdbc2Statement.setObject (AbstractJdbc2Statement.java:1934)` | 2017-12-06T18:16:38.000456 | Marcos |
clojurians | clojure | (but then we have our app servers and DB servers all set to UTC and our MySQL DB configured to run in UTC as well -- pretty much the only sane setup!) | 2017-12-06T18:16:53.000198 | Daniell |
clojurians | clojure | Seriously? The PostgreSQL JDBC driver can't convert from a Java Date to a timestamp with time zone? Wow... | 2017-12-06T18:17:28.000085 | Daniell |
clojurians | clojure | =-( | 2017-12-06T18:17:44.000273 | Marcos |
clojurians | clojure | Then try `tc/to-sql-time` which will produce a `java.sql.Timestamp` instead... | 2017-12-06T18:18:16.000490 | Daniell |
clojurians | clojure | Hurray. this works.
_btw, it was very dumb to confuse with to-sql-date and to-sql-time_ | 2017-12-06T18:20:47.000090 | Marcos |
clojurians | clojure | thx <@Daniell> and <@Rebeca> | 2017-12-06T18:20:58.000221 | Marcos |
clojurians | clojure | Nah, not dumb. Java's various dates and date/times are ... peculiar and annoying. | 2017-12-06T18:21:42.000246 | Daniell |
clojurians | clojure | <@Wilda> If you knew in advance that you wanted to generate random elements from the _same_ set many times, you could improve performance by creating a vector of the set elements one time, then calling rand-nth on that vector many times. That doesn't improve performance if you only want to do it once per set, though. | 2017-12-06T19:49:45.000104 | Micha |
clojurians | clojure | I send message lost yesterday:cry:. I’m beginner and I just start use idea tool, thanks for your help, I will learn it. | 2017-12-06T21:13:58.000081 | Lisabeth |
clojurians | clojure | Is there going to be a state of Clojure survey this year? | 2017-12-06T21:57:42.000124 | Shira |
clojurians | clojure | Yeah, we may slip into the new year. Kind of focused on 1.9 | 2017-12-06T22:54:08.000048 | Sonny |
clojurians | clojure | `(swap! some-atom func)`
suppose func decides to throw an exception (i.e. it can't do the update), what is the proper way to signal this ? | 2017-12-07T00:46:33.000046 | Berry |
clojurians | clojure | <@Berry> throw the exception | 2017-12-07T05:48:41.000261 | Beulah |
clojurians | clojure | i'm using an agent to queue tasks, and want to wait on the task to complete, what is the proper way to do this? | 2017-12-07T07:28:34.000272 | Jena |
clojurians | clojure | i'm now using this: ```(let [p (promise)
a (agent 0)
task-fn (fn [x] (let [new-val (inc x)]
(deliver p new-val)
new-val))]
(send a task-fn)
@p)``` | 2017-12-07T07:29:57.000422 | Jena |
clojurians | clojure | but this delivers the promise before the task fn completes, so it not completely waterproof | 2017-12-07T07:31:37.000365 | Jena |
clojurians | clojure | in theory, it could happen that `(not= @p @a)` | 2017-12-07T07:32:09.000108 | Jena |
clojurians | clojure | <@Jena> you can't make waterproof assumptions on an agent deref | 2017-12-07T07:36:37.000114 | Rosia |
clojurians | clojure | <@Jena> could you use core.async for this case ? | 2017-12-07T07:37:27.000307 | Jami |
clojurians | clojure | Use `await` or `await-for` | 2017-12-07T08:00:09.000402 | Sonny |
clojurians | clojure | i only need to wait until the submitted task completes, with await it would wait for all dispatched tasks | 2017-12-07T08:13:54.000284 | Jena |
clojurians | clojure | maybe an agent is not the right solution for my problem, i'll think about it | 2017-12-07T08:14:44.000387 | Jena |
clojurians | clojure | Found a solution: i can add watch, and pass the delayed deliver to it. As watches are called after the state is updated, this ensures that once the promise is delivered, the task has updated the agent state | 2017-12-07T08:31:02.000021 | Jena |
clojurians | clojure | ```(let [p (promise)
a (add-watch (agent {:x 0}) :force-deliver (fn [_ _ _ new-val] (force (:delayed-deliver new-val))))
task-fn (fn [{:keys [x]}]
(let [new-val (inc x)]
{:x new-val
:delayed-deliver (delay (deliver p new-val))}))]
(send a task-fn)
[@p @a])``` | 2017-12-07T08:31:16.000107 | Jena |
clojurians | clojure | that doesn't guaranteed the state has not been updated by another task meanwhile | 2017-12-07T08:35:03.000114 | Rosia |
clojurians | clojure | true, but thats acceptable for my use case | 2017-12-07T08:35:12.000361 | Jena |
clojurians | clojure | I would like some advice about bytecode generation.
I have a java class with a public primitive int field I want to assign with `set!`, however I can't manage to get rid of intermediate boxing no matter what I hint.
The decompiled bytecode for assignment is always something like :
```
((TheClass)the_instance).the_field = RT.intCast((Number)Numbers.num(value));
```
This looks suboptimal, I'm not sure the runtime is clever enough to bypass this kind of stuff. Am I missing something ? | 2017-12-07T09:57:37.000130 | Rosia |
clojurians | clojure | you'll have to show us the code that's producing that | 2017-12-07T10:10:21.000734 | Kareen |
clojurians | clojure | <@Marcos> you probably solved it already, but take a look at `select*` instead of `select`, it returns a query object that can easily be composed later | 2017-12-07T10:13:46.000431 | Xavier |
clojurians | clojure | and then realized with `exec` | 2017-12-07T10:14:05.000257 | Xavier |
clojurians | clojure | ```(select tbl
(where conditions)
(fields ...))```
```(-> (select* tbl)
(where conditions)
(fields ...))
``` | 2017-12-07T10:15:00.000157 | Xavier |
clojurians | clojure | you can put parts of queries in functions
```
(defn where-thing-active
[query]
(where query ({:expires [> (sqlfn :now)]
:deleted [= nil]})))
```
and then compose them easily like
```(-> (my-base-select)
(where {:user_id user-id})
(cond-> only-active? where-thing-active
type (where {:type (-> type name upper-case)}))
exec))``` | 2017-12-07T10:17:38.000317 | Xavier |
clojurians | clojure | <@Xavier>, thanks! | 2017-12-07T10:17:55.000501 | Marcos |
clojurians | clojure | here is a minimal example
<https://gist.github.com/leonoel/b7e8e4b93e7d14fcbdd3fbdac4921223> | 2017-12-07T10:32:46.000595 | Rosia |
clojurians | clojure | use unchecked-inc-int | 2017-12-07T10:35:23.000410 | Kareen |
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