fastmath vec2/vec3/vec4 dosn't render and causes exception

[genmeblog]

Hi, with the latest nextjournal (0.5.346) following code results in exception and renders as nil value. Maybe something is wrong with fastmath.vector implementation however I can't understand what.

(ns sometest
  (:require [fastmath.vector :as v]))

(v/vec2 3 4)
;; => #vec2 [3.0, 4.0]

(comment
  (require '[nextjournal.clerk :as clerk])
  (clerk/build-static-app! {:out-path "docs" :paths ["src/sometest.clj"]}))

The html is generated and prints nil as a vec2 value:

And exception is like:

#error {
 :cause class clojure.lang.Keyword cannot be cast to class java.lang.Character (clojure.lang.Keyword is in unnamed module of loader 'app'; java.lang.Character is in module java.base of loader 'bootstrap')
 :via
 [{:type java.lang.ClassCastException
   :message class clojure.lang.Keyword cannot be cast to class java.lang.Character (clojure.lang.Keyword is in unnamed module of loader 'app'; java.lang.Character is in module java.base of loader 'bootstrap')
   :at [clojure.lang.RT uncheckedIntCast RT.java 1476]}]
 :trace
 [[clojure.lang.RT uncheckedIntCast RT.java 1476]
  [fastmath.vector.Vec2 invoke vector.clj 365]
  [fastmath.vector.Vec2 valAt vector.clj 352]
  [clojure.lang.RT get RT.java 760]
  [nextjournal.clerk.viewer$var_from_def_QMARK_ invokeStatic viewer.cljc 163]
  [nextjournal.clerk.viewer$var_from_def_QMARK_ invoke viewer.cljc 162]
  [nextjournal.clerk.viewer$wrapped_with_viewer invokeStatic viewer.cljc 293]
  [nextjournal.clerk.viewer$wrapped_with_viewer invoke viewer.cljc 280]
  [nextjournal.clerk.viewer$describe$fn__18862 invoke viewer.cljc 375]
  [nextjournal.clerk.viewer$describe invokeStatic viewer.cljc 375]
  [nextjournal.clerk.viewer$describe invoke viewer.cljc 366]
  [nextjournal.clerk.viewer$describe invokeStatic viewer.cljc 372]
  [nextjournal.clerk.viewer$describe invoke viewer.cljc 366]
  [nextjournal.clerk.view$__GT_result invokeStatic view.clj 110]
  [nextjournal.clerk.view$__GT_result invoke view.clj 109]
  [nextjournal.clerk.view$describe_block invokeStatic view.clj 164]
  [nextjournal.clerk.view$describe_block invoke view.clj 151]
  [clojure.core$partial$fn__5859 invoke core.clj 2635]
  [clojure.core$map$fn__5880$fn__5881 invoke core.clj 2746]
  [clojure.lang.PersistentVector reduce PersistentVector.java 343]
  [clojure.core$transduce invokeStatic core.clj 6885]
  [clojure.core$into invokeStatic core.clj 6901]
  [clojure.core$into invoke core.clj 6889]
  [nextjournal.clerk.view$doc__GT_viewer$fn__22748 invoke view.clj 171]
  [clojure.core$update invokeStatic core.clj 6185]
  [clojure.core$update invoke core.clj 6177]
  [nextjournal.clerk.view$doc__GT_viewer invokeStatic view.clj 171]
  [nextjournal.clerk.view$doc__GT_viewer invoke view.clj 167]
  [nextjournal.clerk$file__GT_viewer invokeStatic clerk.clj 274]
  [nextjournal.clerk$file__GT_viewer invoke clerk.clj 271]
  [nextjournal.clerk$file__GT_viewer invokeStatic clerk.clj 273]
  [nextjournal.clerk$file__GT_viewer invoke clerk.clj 271]
  [clojure.core$juxt$fn__5840 invoke core.clj 2598]
  [clojure.core$map$fn__5880$fn__5881 invoke core.clj 2746]
  [clojure.lang.PersistentVector reduce PersistentVector.java 343]
  [clojure.core$transduce invokeStatic core.clj 6885]
  [clojure.core$into invokeStatic core.clj 6901]
  [clojure.core$into invoke core.clj 6889]
  [nextjournal.clerk$build_static_app_BANG_ invokeStatic clerk.clj 380]
  [nextjournal.clerk$build_static_app_BANG_ invoke clerk.clj 366]
  [somtest$eval32629 invokeStatic form-init3528201830096940289.clj 8]
  [sometest$eval32629 invoke form-init3528201830096940289.clj 8]
  [clojure.lang.Compiler eval Compiler.java 7181]
  [clojure.lang.Compiler eval Compiler.java 7136]
  [clojure.core$eval invokeStatic core.clj 3202]
  [clojure.core$eval invoke core.clj 3198]
  [nrepl.middleware.interruptible_eval$evaluate$fn__1231$fn__1232 invoke interruptible_eval.clj 87]
  [clojure.lang.AFn applyToHelper AFn.java 152]
  [clojure.lang.AFn applyTo AFn.java 144]
  [clojure.core$apply invokeStatic core.clj 667]
  [clojure.core$with_bindings_STAR_ invokeStatic core.clj 1977]
  [clojure.core$with_bindings_STAR_ doInvoke core.clj 1977]
  [clojure.lang.RestFn invoke RestFn.java 425]
  [nrepl.middleware.interruptible_eval$evaluate$fn__1231 invoke interruptible_eval.clj 87]
  [clojure.main$repl$read_eval_print__9110$fn__9113 invoke main.clj 437]
  [clojure.main$repl$read_eval_print__9110 invoke main.clj 437]
  [clojure.main$repl$fn__9119 invoke main.clj 458]
  [clojure.main$repl invokeStatic main.clj 458]
  [clojure.main$repl doInvoke main.clj 368]
  [clojure.lang.RestFn invoke RestFn.java 1523]
  [nrepl.middleware.interruptible_eval$evaluate invokeStatic interruptible_eval.clj 84]
  [nrepl.middleware.interruptible_eval$evaluate invoke interruptible_eval.clj 56]
  [nrepl.middleware.interruptible_eval$interruptible_eval$fn__1264$fn__1268 invoke interruptible_eval.clj 152]
  [clojure.lang.AFn run AFn.java 22]
  [nrepl.middleware.session$session_exec$main_loop__1334$fn__1338 invoke session.clj 218]
  [nrepl.middleware.session$session_exec$main_loop__1334 invoke session.clj 217]
  [clojure.lang.AFn run AFn.java 22]
  [java.lang.Thread run Thread.java 833]]}

[mk]

Can you try the attached fix? The problem was that (get (fastmath.vector/vec2 3 4) :nextjournal.clerk/var-from-def) throws and the code assumed it would not.

[genmeblog]

Tried and fix is working. Thank you very much!

[borkdude]

I would say their ILookup implementation is wrong :).

[genmeblog]

@borkdude oh! can clarify you why?

[borkdude]

ILookup should not throw when a key/index is not present.

user=> ([1 2 3] 3) ;; this is how you probably implemented it
Execution error (IndexOutOfBoundsException) at user/eval143 (REPL:1).
null
user=> (get [1 2 3] 3) ;; this is how it should behave
nil

[genmeblog]

It doesn't throw:

(def v (fastmath.vector/vec2 1 2))

(v 3)
;; => nil

(get v 3)
;; => nil
(get v 3 :not-found)
;; => :not-found

(sorry for offtopic)

[borkdude]

Oh, then I misunderstood the issue, sorry.

[borkdude]

@genmeblog Why does:

(get (fastmath.vector/vec2 3 4) :nextjournal.clerk/var-from-def)

throw? I don't think it should throw.

[genmeblog]

Oh. Indeed! Got it. Thanks!

[genmeblog]

Hmmm @mk I think you should revert the change. get works on many types other than map itself. Looks like I misunderstood the contract for ILookup. I'm fixing it now on my side.

[mk]

@genmeblog think the change should stay anyway. As we've seen, it can cause problems with code that's out there and being more defensive here doesn't hurt.