Should I be using spec’s s/valid? or s/assert in my pre/post conditions?

s/assert seems more useful, but maybe I’m doing it wrong

@jings.bill :pre/`:post` conditions -- makes more sense to me to use a predicate (`s/valid?`). I personally don't like :pre/`:post` conditions and I don't much like assertions. If I want argument checking in dev/test, I'd rather use s/fdef and instrumentation. When I want to check data for validity -- and handle that as part of my design -- I'll use s/valid? (or s/conform) in production code inside the function.

Ahh. I had no idea that was what fdef did.

Good saturday morning everyone. I'm trying to start refactoring a file, for the first time. I want to have some core functions, some testing infrastructure functions, some functions which use the core and testing infrastructure, and also some utility functions. Currently all functions are defined in the same core file, and I want to distribute the functions to the appropriate other files. As I understand the tooling for closure requires that I decare one namespace per file, whereas in Common Lisp I'd declare one namespace and have several files just use that name space with the equivalent of in-ns

The structure should be core requires util, util requires nothing, tester requires nothing, rte-tester requires tester and core.

When I create a file named rte_tester.clj which declare no function but begins with

(ns  clojure-rte.rte-tester
  (:require [clojure-rte.tester :refer :all]
            [clojure-rte.core :refer :all]
            )
  (:gen-class))

Syntax error (IllegalStateException) compiling at (rte_tester.clj:1:1).
random-test already refers to: #'clojure-rte.core/random-test in namespace: clojure-rte.rte-tester

I already restarted cider a couple of times, and that doesn't help.

It is certainly common to have a one-to-one correspondence between file and Clojure namespaces, and some tools do expect that. It isn't a requirement of the language implementation itself, though. I wouldn't veer away from that unless you were curious whether the tooling you are using handles it, and/or really really prefer otherwise.

@andy.fingerhut yes, i was trying to embrace the standard advice and do just that. But having trouble understanding how to do it. Is there something wrong with that (ns ...) expression at the top of an otherwise empty file?

I would recommend leaving out (:gen-class) unless you know for a fact that you absolutely need it for some reason.

OK, I don't even know what :gen-class does, lein just put it in the original file and I copied it.

What does it mean?

It directs the Clojure compiler to create a Java class file with some particular Clojure-specific conventions for some things. It isn't typically needed. I can't answer in any great detail because I have so rarely encountered it.

I thought it was probably related to making a standalone application, unix level application. Because lein also defined a -main function

Do you define a function random-test in any of those namespaces?

Even if I take out the :gen-class

I define random-test only in the core. and I'm NOT redefining it in this file.

Clojure on Java will look for compiled JVM byte code in files whose names end in .class on the JVM class path, and use those if they exist, and I think there is another condition like their time stamp must be more recent than a corresponding file with suffix .clj or .cljc . Depending on the tooling you are using, there may be old .class files around created from before the time you moved functions from one namespace to another.

Deleting all of those and starting a fresh JVM could help in that case

I believe lein clean may do that, but you can also use Unix-y commands like find to check if you want to be certain

Here are the three files.

Can you take a look at the files and see if there's something obvious wrong.

I tried lein clean, and then restart-cider, but same problem occurs.

Are all of those files in a directory named clojure_rte , and that directory is inside of a directory named src in the root of your project?

When I put those files into a directory src/clojure_rte of a project template that I created using lein new clojure_rte , and then run the command lein repl , I do not see the error you showed above, but I do see other errors, e.g. warnings about vars with names having asterisks around them, but not declared dynamic (that is only a warning), but also an error about unable to resolve traverse-pattern

I did not use CIDER to get that result, just lein repl command in a terminal, in project root dir

It does appear that there is a call in your core.clj source file to traverse-pattern before it is defined.

OK, it sounds like I'm on the right track, there must be something cached somewhere.

I am not claiming that is the root cause of the behavior you are seeing, which sounds like something else. I don't use CIDER, so am not a good person to try to reproduce that aspect of it.

called before defined, yes that's something I need to work through,

it was one reason to separate into seperate files. to get a better handle on what requires what.

sure, there are typically a flurry of errors while you reorganize things

it would be cool if the clojure compiler would internally perform a topological sort of the top level forms before compiling the file.

how did you fine the used before defined? was that a warning by the loader. I don't see it.

You can use (declare traverse-pattern) early in a file if you like the order things exist in, and such a thing is necessary for mutually recursive top level functions.

this one is not mutually recursive, I'll re-order it. But how did you find it?

I saw an error message about traverse-pattern in the output of the lein repl command I typed with a fresh lein new clojure_rte template, plus your 3 files copied into src/clojure_rte directory.

I don't see any warning.

ahh, it's something which lein found, not something that load/compile found.

how am I supposed to name top level variable definitions if not *something* ?

(a) You can ignore the warnings. They are harmless. (b) You can leave off the 'earmuffs'. (c) If you want dynamically bindable Vars, you can use (def ^:dynamic *something* ...)

Cool, I marked them dynamic for now. I need to figure out later whether they should be dynamic or not.

Not sure if you saw replied in a thread above about error messages I saw on my system. I put them there because they include a fairly long chunk of text

I am not sure, but I suspect with your familiarity with Common Lisp, and newness to Clojure, you are probably feeling like an American in the UK, occasionally using words you think are harmless but offend people, or vice versa 🙂

Did I say something offensive? Sorry. 😞

we nerds sometimes get too excited with technical things.

I did recently accidentally find the clojure function cl-format I laughed.

i'm curious how complete it is. cl-format is a dsl unto itself.

https://clojure.github.io/clojure/doc/clojure/pprint/CommonLispFormat.html

@ahmed1hsn are you a cl-format user?

Where's a good place to pose cider related questions. I don't see a #cider channel here

Actually there is a #cider channel

in a (cond ...) we have a sequence of test consequent pairs, if test is true, then cond evaluates to the consequent, if not, the next test is considered ... is there a way to tell cond for a particular consequent I just want to return the value of the test?

if not, this might be my first excuse to write a clojure macro, cl-cond I see there is a https://stackoverflow.com/questions/4128993/consolidated-cond-arguments-in-clojure-cl-style with a buggy macro implementation provided. Here is my suggested solution

(defmacro cl-cond [[if1 then1] & others]
  ;; implementation from
  ;; 
  (when (or if1 then1 others)
    (let [extra-clauses# (if others `(cl-cond [email protected]))]
      (if then1
        `(if ~if1 ~then1 ~extra-clauses#)
        `(or ~if1  ~extra-clauses#)))))

Why does this fail: (doc (first (apropos "run"))) but this succeed? (doc clojure.core/dorun)

Lots of functions in clojure take a predicate. Is there a function to logically invert a predicate? For example

(filter (logically-invert seq?) items)

found it! its called complement

@sfyire doc is a macro which expects an unquoted symbol, not the list (first (apropos "run")) , which the doc macro will not evaluate

doc calls a function in its implementation, which you could call from the REPL, but it isn't exactly convenient to type in its built-in form, although you could of course write your own function that makes it more convenient.

(let[n(read-string(first *command-line-args*))](print(and(> n 1)(=(reduce #(* %1(if(=(mod n %2)0)0 1))1(range 2 n))1))))

Can anyone please help?

cljs.user=> (apropos "read")
(cljs.core/*print-readably* cljs.core/spread)

cljs.user=> (require '[clojure.edn :as edn])
nil
cljs.user=> (dir edn)
read
read-string

Can I destructure a vector and give it a name?

I want to generate some random data that has one decimal point, as a number type rather than a string. If I wanted a string, I'd use format . I can use rand to generate random decimal numbers, but only want one decimal place. Wrapping with float gives too many decimal places. Math/round returns a whole number, with-precision doesn't truncate the number of decimal points... Any suggestions (I dont care about rounding errors, its mock data). Thank you.

Can you generate strings and then parse into floats?

There was a very nice one-liner in the thread that suits me. I also tried DecimalFormat Java class, but its still a string and a lot of code. Had to remember how to do Java Interop for about 30 seconds 🙂

(import java.text.DecimalFormat)

(def decimal-format 
  (DecimalFormat. "#.#"))

(.format decimal-format (rand 20))

when I'm using :keys destruction on a map, can I still get the whole structure ?

ok, I can use the :as key

is there a way to convert a string UUID to the UUID type?

postgresql is yelling at me since the JSON is passing in a stringified uuid

UUID/fromString

just came across this as well

thanks @hiredman!

java.util.UUID cannot be cast to clojure.lang.IFn hmm

:thinking_face:

my function looks like this

(update-in item [:seller_id] (java.util.UUID/fromString (get item "seller_id")))

when i do (println (type (get item "seller_id"))) it says the type is string tho

what you are trying to do is assoc-in , not update-in

will assoc-in dup the value though?

or maybe i do not have a full grasp of when to use update-in

yeah i get this error from psql then

org.postgresql.util.PSQLException: ERROR: column "seller_id" specified more than once| Position: 66

because you're specifying it twice, once as a string key "selled_id", and once as your new keyword key :seller_id

yeah it just adds another key of the same name

{name Burton Board, description Snowboard, price 100, quantity 1, seller_id 8e85d9c3-c800-4d03-b79c-286343ad6020, :seller_id #uuid "8e85d9c3-c800-4d03-b79c-286343ad6020"}

oh

OHHH

gah! idk why ring gives me the body like that vs everything as a keyword

what you probably mean to do is update item "seller_id" #(java.util.UUID/fromString %) , or something like that

what does % mean in this situation?

cause what you wrote is a million times more readable haha

https://clojure.org/guides/learn/functions#_anonymous_function_syntax

cool! ill have to read up on that

also using update gives me the original error i was having of java.lang.ClassCastException: java.util.UUID cannot be cast to clojure.lang.IFn

worth noting that you have to wrap in an anonymous fn only because it's a Java method, for regular Clojure functions you can just pass it in like (update item "seller_id" from-string)

oh

wow ok mind blown

after you said that yuhan

i copied and pasted dmitry's code and it works

your explanation makes sense

yup, if it helps you can think of (update m k f) <=> (assoc m k (f (get m k)))

thank you @jason358 and @qythium

Is there a simple way to get a formatted version of a map?

I'm imaginging somethign like pprint, but not tied to any output. Just a fancy string

nvm, solved my own problem. In cljs, it's (with-out-str (cljs.pprint/ppring coll))

I’m loading a file in a fresh REPL, and it’s failing to find a dependency:

Syntax error compiling at (src/gascan/posts.clj:1:1).
namespace 'gascan.post-spec' not found

(ns gascan.post-spec
  (:require [clojure.spec.alpha :as s]))

If you start a REPL, is it automatically loading some namespaces, or no? If not, maybe you could try (require 'gascan.post-spec) as the first thing in the new REPL and see if there are any errors?

hmm, no errors. but the file still fails to load.

gascan.core> (require 'gascan.post-spec)
nil
gascan.core> (ns-interns 'gascan.post-spec)
Execution error at gascan.core/eval15313 (form-init6807784250795486954.clj:46).
No namespace: gascan.post-spec found

My mind isn't jumping to any theories about why that might happen...

Any stale .class files around you can try deleting? Other cached stuff? Try a fresh git clone of the same project on a different machine? etc.?

The fact that your REPL prompt is gascan.core makes me wonder whether when you typed (require 'gascan.post-spec) it has already earlier tried to do that, and failed, and your require is doing nothing.

Might give more info or error if you can make (require 'gascan.post-spec) be the first thing that Clojure does in the new JVM

that was it

i put together a deps.edn so I could fire up a bare clj REPL (`lein repl` loads a lot of stuff right at the bat)

user=> (require 'gascan.post-spec)
Syntax error compiling at (gascan/post_spec.clj:4:10).
No such namespace: java-time

that was very confusing. not the first time i’ve been confused by errors in cold start loading my REPL. is there a better place to find those errors than in the REPL itself?

There are at least a dozen different ways to start a Clojure REPL. Where error messages go in each case can differ. I would check carefully the output of your earlier attempts to see if there was no such error message anywhere, and if not, maybe describe how you start your REPL, and people familiar with that way of doing it might know.

I’m starting it with a leiningen project in cider. The main REPL window doesn’t show any errors

In general, Leiningen has more stuff it tries to do for you under the hood, and so the #leiningen channel is a good place to find people expert in what kinds of things can cause this behavior, but it is so widely used that this shouldn't be a bad channel to ask, either.

You could try asking in #cider channel if startup errors maybe go to some other Emacs buffer, perhaps.

Great. Thanks!

Hello Clojurians, I've tried to update the db in re-frame in this inelegant way

(re-frame/reg-event-db
          :getTagValue
          (fn [db [_ data]]
            (assoc-in db [:tag-table :foo :current] (data "value"))
            (assoc-in db [:tag-table :foo :unit] (data "unit"))
            (update-in db [:tag-table :foo :history] conj (data "value"))))

(update-in db [:tag-table :foo] magic-function-that-updates-3-values-at-once data)

If so I am a little confused about how to write it, maybe someone can give me a tip?

Thanks in advance!

assoc-in and update-in don't mutate db. They return a new db value. So you're computing new db values and only returning the result of your call to update-in.

A common way to chain together changes to a map is the thread-first macro ->. Your event should work the way you expect if you formulate it as

(re-frame/reg-event-db
  :getTagValue
  (fn [db [_ data]]
    (-> db
      (assoc-in [:tag-table :foo :current] (data "value"))
      (assoc-in [:tag-table :foo :unit] (data "unit"))
      (update-in [:tag-table :foo :history] conj (data "value")))))

That's syntactic sugar for the very difficult to read

(re-frame/reg-event-db
  :getTagValue
  (fn [db [_ data]]
    (update-in (assoc-in (assoc-in db [:tag-table :foo :current] (data "value")) [:tag-table :foo :unit] (data "unit")) [:tag-table :foo :history] conj (data "value"))))

The important part of that is that each operation is being done on the result of the previous one, rather than just on db.