if i'm requiring a library with a defrecord and aliasing it is there any reason (alias/recordName. foo bar) would throw a "Unable to resolve classname" error?

@sophiago defrecord creates a class named recordName, and a couple of functions ->recordName etc. the class is a java class, referenced the normal java way, so doesn't get nice namespaces and aliases etc

so if you want to use the java interop constructor recordName. then you need to import the class. but you can use the generated functions, ->recordName and map->recordName through their namespace aliases etc

@bfabry i'm not sure i understood all that. are you saying i can just use import or do i need to actually use java interop functions... because the latter would obviously be horrible

@sophiago generally I'm pretty bad at explaining this stuff, so you may want to seek out some documentation on defrecord. the short story of it is you do not need to use java interop for defrecords, because you can use the automatically generated functions. alias/->recordName will do what you expect alias/recordName. to do

it's ok. i'm pretty sure you just mean to import them

you cannot use alias/recordName., because that's java interop sugar, imagine it gets expanded to (new alias/recordName), which doesn't make sense, because you can't alias class names

you can do (recordName., which gets expanded to (new recordName) if you import that class name, like you can with other class names

right

personally, I would strongly recommend just using the automatically generated functions, so that you get the nice aliases etc and all the goodness that namespaces provide, and don't need to deal with interop land

and i can't use :refer when i require the library either? i need separate import statements?

you can use :refer to :refer the function ->recordName, but you cannot refer a class name

yeah none of this is making sense to me

you're saying in one sentence i can do something and then next i can

the class is a the record

sorry

typo

defrecord creates a class as far as the error codes are concerned

ok

so saying i can refer a record, but not a class doesn't make any sense in this situation

there are no java classes

only constructors i created with defrecord

the stuff in require works on clojure stuff, basically. functions. so you can alias/refer the functions ->recordName and map->recordName. you cannot do anything with classes in require. so you cannot refer recordName. or (new recordName). if you want to use a class, which is what recordName is, then you need to either use its fully qualified package and class name, or you need to import it and use just the bare class name (normal java rules)

a record is a class

what's confusing about your explanation is that "a record" is "clojure stuff"

defrecord creates a class that inherits some useful functionality, and a bunch of functions for working with objects of that class

i think i understand what you're saying though

i'm not doing any java interop

to be clear

the syntax Foo. is java interop

that's just syntax

yes, it expands to (new Foo) which is java interop

it's not java tho

user=> (macroexpand '(Foo.))
(new Foo)

it is definitely java. the new form expects a class

i understand what you're saying

it's just a confusing way of putting it

sorry, like I said I'm not the best at explaining

java interop refers to interop with java

whereas this is purely clojure

i do understand you tho

i cannot use :refer right?

only import?

you can use :refer to :refer ->recordName and map->recordName, if you want to reference the class recordName directly then you must use :import

ok, that part i still don't understand

also even if i use import i'm unclear on how to qualify it so as not to use the full ns the whole time

why don't i just use code examples

same as java, you must either use a fully qualified classname, or import the class from the package and use the bare classname

(defrecord Rational [numerator denominator])

so that's one of my classes

and so far i'm requiring the library like this:

(:require [symbolic-algebra.core :as sym])

inside my ns obviously

so the errors were from trying to be like : sym/Rational.

i know now why that doesn't work

😆 I think I can see where this is going and you're going to be annoyed

no i think it's ok

i can either use refer or import

i would just prefer to not be like this:

symbolic-algebra.core/Rational.

every time!

so, given that require statement you can use (sym/->Rational arg arg arg) and (sym/map->Rational {:arg1 arg1 :arg2 arg2})

you can also use (symbolic_algebra.core.Rational. arg arg arg)

what?

the arrow syntax?

that's it?

or, you could add the :import (:import (symbolic_algebra.core Rational)) and use (Rational. arg arg arg)

wait.... this whole time you were just trying to tell me i could use that arrow syntax instead?

the arrow isn't syntax, when you define a record you automatically get two functions created in that namespace, ->Rational and map->Rational for creating records of that type. and yes I was 🙂

and you're using extra args... that's a mistake right?

mine is just dyadic

sorry yes I didn't pay attention to the definition. substitute in the right amount of args you need

ok just wanted to be sure

wow after all that!

haha

ok lemme try it to be certain

it worked! thanks!

i never realized that about records

<-not a /Java coder

of course now i have other errors, but i'll figure them out

oh, because i need to do this with other records

oh, when it prints tho...it shows up with the full ns, which is quite long

i suppose that's a reason to alias it 😕

when it prints the object? mm yes

if i add that to my require it will change how it prints?

I'm actually not sure

if I wanted to change how a record prints I would override print-method for that object type

oh...how do i do that?

or could i do that for the whole library?

right now it's just printing the whole library name and i can barely read the list output

actually sorry, I mean toString

I really don't know much about the clojure printing ecosystem

=/

docs say toString is for deftype not defrecord

hmmm

here it is https://clojuredocs.org/clojure.core/print-method

ah ok, i was just going to say i think i found how to do it 🙂

user=> (defrecord Foo [bar]
  #_=>   Object
  #_=>   (toString [self] (str "A[" bar "]")))
user.Foo
user=> (->Foo "blah")
#user.Foo{:bar "blah"}
user=> (defmethod print-method Foo [v ^java.io.Writer w] (.write w (str "A[" (:bar v) "]")))
#object[clojure.lang.MultiFn 0x7e0ba804 "clojure.lang.MultiFn@7e0ba804"]
user=> (->Foo "blah")
A[blah]
user=>

so the toString stuff doesn't work, adding a print-method does

woah, i never would have figured this java io stuff out

seems you just substitute in whatever string you want tho

yup

it's just boilerplate really. the print-method needs to take a writer rather than just returning a string, so that it can work efficiently if you're writing many objects to a file or whatever. the ^java.io.Writer bit is just there to tell the compiler the type of that object so that it doesn't need to figure it out at runtime (slow), and write is just the method on the writer that takes a string

and it's always v and then w?

the v is the value passed in, in this case the instance of Foo

sorry I copypasted, I should've given them better names

oh. i just assumed that was boilerplate

[record ^java.io.Writer writer] would be better

that's how I got the value "blah" out of the object. (:bar v)

the docs aren't very helpful 😛

haha, which docs? I agree with the print-method stuff. tracking that down was tricker than I expected

ha, i guess they're no docs

and i'm talking about user created docs on the cheatsheet

there is a link to read about the reader

if i was less tired and looking for a quick fix i suppose

@bfabry ok, i realized i have to declare a defmethod with print-method in addition to defrecord...i was just putting it inside the defrecord

ah sorry, yes they're different things. defmethod is adding a method to the multi-method print-method (try saying that 10x fast)

well, i realized because i found this: http://stackoverflow.com/questions/15179515/pretty-printing-a-record-using-a-custom-method-in-clojure

but the implementation there seems off

instead of .write it just repeats print-method?

and uses a key instead of a string?

still doesn't seem to matter what variable you match between them tho

x... v... whatever?

it's an argument list for the method, you can name them whatever you want. it's their order that determines what they are

and i assume .write with a string is what i want, not what's in that SO question...

what they have will work too... they're calling the print-method multimethod again, this time with the first argument being a String, so it will dispatch to the print-method definition meant for handing strings

ah ok

i think i'll do it the docs way

hmm...no errors but not working in the repl

@bfabry it's like this?

(defrecord Rational [numerator denominator])

(defmethod print-method Rational [v ^java.io.Writer w] (.write v "%"))

?

basically i have a bug in code that uses this library i can't even diagnose until i get it to pretty print!

but i'm testing it from the library repl itself

the default printing behaviour won't work in the meantime? I think you'll want (.write w (str (:numerator v) "%" (:denominator v)))

ah ok

the problem right now is it prepends the ns

so output is:

#symbolic_algebra.core.Rational{:numerator 3, :denominator 4}

when i have a whole list of a dozen of those it makes it hard to diagnose typing errors

fair

hmm...behavior is the same

it's like it doesn't even recognize the defmethods at all

how are you printing the values?

oh...does this just apply to print and println and such?

this is in the repl

like this:

(add (Rational. 1 2) (Rational. 1 4))

it should work in the repl. but it won't work with pprint

no, i never use pprint

seems to work for me

user=> (defrecord Rational [numerator denominator])
user.Rational
user=> (defmethod print-method Rational [v ^java.io.Writer w] (.write w (str (:numerator v) "%" (:denominator v)))
  #_=> )
#object[clojure.lang.MultiFn 0x7e0ba804 "clojure.lang.MultiFn@7e0ba804"]
user=> (Rational. 1 2)
1%2
user=>

ugh

this is near the top of my code too 😕

wait

i mean, it makes sense you wouldn't have an ns in front of it since it's the user repl

my thing is being able to get rid of that

user=> (in-ns 'foo)
#object[clojure.lang.Namespace 0x76d36d2d "foo"]
foo=> (user.Rational. 1 2)
1%2

i don't know what could be doing this. i get:

#symbolic_algebra.core.Rational{:numerator 1, :denominator 2}

have you defined the record more than once in the same repl session?

there's known issues with that

no, i just exited to be sure

i do have a def-protocol

user=> (defrecord Rational [numerator denominator])
user.Rational
user=> (defmethod print-method Rational [v ^java.io.Writer w] (.write w (str (:numerator v) "%" (:denominator v)))
  #_=> )
#object[clojure.lang.MultiFn 0x7e0ba804 "clojure.lang.MultiFn@7e0ba804"]
user=> (Rational. 1 2)
1%2
user=> (in-ns 'foo)
#object[clojure.lang.Namespace 0x76d36d2d "foo"]
foo=> (user.Rational. 1 2)
1%2
foo=> (in-ns 'user)
#object[clojure.lang.Namespace 0xc9941a6 "user"]
user=> (defrecord Rational [numerator denominator])
user.Rational
user=> (Rational. 1 2)
#user.Rational{:numerator 1, :denominator 2}

and use extend-type with those

(the class id on the Rational changes because it was def'd again)

ah

but like i said, i exited

do you want to post your code in a gist somewhere?

sure

@sophiago: printing works fine for me when I paste that into my repl

yeah that looks fine

@sophiago: here's a way to reproduce what I'm getting

take that file, add (println (Rational. 3 4)) to the bottom of it

then run java -jar ~/.m2/repository/org/clojure/clojure/1.8.0/clojure-1.8.0.jar that-file.clj

hold on one sec

sorry I gotta grab some lunch

np thanks

ok lemme try that @gfredericks

@gfredericks did you intend for me to put that in a -main?

because otherwise i get no output except the warnings for overridden built-ins

i could just put it in the -main and use lein run?

@sophiago: sure, try that

I only got output if I put it outside the main

i get no output either way tho...

which is odd because i should be getting output at least

@sophiago: and you're running java just the way I have it above?

well, i replaced that-filed with the filename...

but otherwise yes

that's pretty spooky then

ugh

yikes

this is not good

if you point it at a file that just has (println "what") in it, does that work?

i do regularly print things

the reader works on my system

i'm trying to think what else could be causing this

oh wait...

something stupid

omg

git branches

fuck hold on

yup

idk what the lesson is here even

naming convention something something i guess?

i spent like 45 minutes editing one file in emacs that i thought was in an adjacent directory i had cloned

i should have just changed the name to something totally different, although not sure that would have helped as it would have only been the outer dir

yikes...sorry for wasting everyone's time

well thanks for the help @gfredericks and @bfabry

time for me to sleep i think 😛

no worries, glad you got it sorted

not a waste of time more than any other question; presumably trying the most basic thing and having it not work helped you think of alternative causes

is there a way in leiningen to have it move files to target but not add them inside the jar when compiling?

Does anyone here have experience with OrientDB?

@gfredericks Is there an easy way to make a monadic for? If not, should there be?

@eraserhd you mean one that magically works for (ha!) any monad?

Perhaps just that I supply bind and return?

e.g. (make-for bind-fn return-fn).

(and get :let)

If you explicitly supply those you can build a for

If you want :when it has to be a MonadPlus I believe

ah, yeah. I've just realized that my use case isn't quite right, though.

To this day I still wonder: is there a way to pithily express: (cond (f x) a (g x) b))

Is there a standard way to express that without repeating x? condp would work if clojure.core had a call function, but it doesn’t, as far as I can tell.

It's not amazingly pretty, but shouldn't

(condp #(%1 %2) x
  f a 
  g b)

Or

(condp apply [x]
  f a
  g b)

could anyone explain me what should the form (doall 1 coll) do?

it forces the first item in coll, which is presumably a lazy seq

imo if you are calling doall with an n, you are probably in a bad place :)

generally, I am suspicious of any case where you have to know much of a lazy seq is realized

@cigitia you can always macro it to make your own control flow that is as pithy as you like

(defmacro condf
  [v & func-rets]
	(let [[f r & more-fs] func-rets]
	  (when f		
	    `(if (~f ~v) ~r (condf ~v ~@more-fs)))))

(condf x f a g b)  ;; no repeated x!
(condf 5 pos? :pos zero? :zero neg? :neg)

@alexmiller are you the sort of person that indents function bodies further than the arglist

just copy/paste cruft

so, no

okay that's good to know

judge me as you will

thanks alexmiller gfredericks , I'm wrapping langohr's get function on a queue to take a subset of it, all of it in a macro that cleans up AMQP connection and its channels, so I need to force it

icky

I'm trying to understand why having both filename.clj and filename.cljc (both using the same namespace) does not work. Only the .clj file is compiled as far as I can tell. Is it a limitation of the current implementation or something that should never work? I ask, because as I understand it, Clojure doesn't really care about files, just top level forms. (As if everything was sent to a REPL) So, given that, it seems like you'd compile both files and put the various def's from both files into the namespace.

hey quick question - has anyone found themselves wanting a for-into as a shortcut for (into X (for …))? e.g. (for-into {} [[k v] {1 2 3 4 4 5} :when (even? v)] {(str k) (inc v)}) => {“1” 3 “3” 5}

@grant Clojure and ClojureScript will both use their platform-specific extension first and fall back to cljc as last choice

this allows you to ship a default (cljc) and platform-specific overrides

in what context are you doing compilation?

@mikekap you could use the into transducer for that

(into {} (comp (filter #(even? (val %))) (map #(vector (str (key %)) (inc (val %))))) {1 2 3 4 4 5})

(hurting for a kv variant there)

@alexmiller I tested against lein and boot to see if I got the same behavior from both. In this particular case I was placing things like specs and validation code in .cljc files and client and server specific code in .cljs and .clj files, respectively. I understand I can make it work by either changing filenames and namespaces or putting it all in a .cljc file. It just didn't match my intuition about how it would work, so I was trying to further my understanding and fix my intuition.

you should fix your intuition :)

@alexmiller yea that’s why i was inclined to go with for - it doesn’t require (fn [[k v]]). I think I have an aversion to typing fn :X

when a file is loaded for a namespace, it will load exactly one file, not a union of files

So the correct structure will always be either filename.cljc or filename.clj and filename.clj[sr].

@alexmiller Thanks for the help Alex.

You can have both cljc and clj

Then you can put a portable for all versions in the cljc and an override for just one platform in clj or cljs or cljr

But you'd have to put all of the def's that you want in the override file, you can not just have an override file that has one or two additional function in it. Right?

i just realized the source of a bug i've been experiencing is that gen-class doesn't map with dependencies. should i just simply copy it over in the namespace since it's quite short or is there anything else people do about this?