Clojurians Log v2

I’m looking to convert some macros for usage with sci. See https://github.com/sicmutils/sicmutils/pull/216. I first tried the copy-var approach, that seemed to work fine from Clojure, but not from ClojureScript. Now I’m trying to convert them but not clear on what I need to do.

@mkvlr Can you make a small example which allows me to explain how to solve that small example?

@borkdude sure, or do you have some good pointers of macros you converted for sci?

@mkvlr sci.impl.namespaces has lots of those.

many of those have _ _ as the first two args, this is how you can find them

in general, a macro is nothing but a function that receives some forms and returns some other forms

but it has two extra arguments: form and env, but often these are not used. so they are named _ _

a common problem with copying macros is that the source macro is defined in a different namespace than the namespace of the sci environment

so the source macro expands into the wrong namespaced symbols

I usually solve this by copying the macro and fully qualifying all symbols myself

oh, but I can use quoting and splicing normally?

yes, but the syntax quote will resolve the symbols into the namespace where the macro is defined. so this is often the mismatch

syntax-quote is handled at clojure read-time, not at sci evaluation time

ok, so just fully-qualify it

so:

(ns foo)
(defn foo [_ _] `x)

and you recommend copying, right? It’s a bit too much of a head-bender for me how this works in ClojureScript with copy-var

copying is done to make the thing a var inside sci, so everything var-related works on it. But sci also allows you to just pass the function reference in the namespaces option

if vars aren't important to your sci usage, then you can just avoid using sci/copy-var

some people (in babashka for example) want to be able to use doc, alter-var-root!, with-redefs, etc

but it will make doc etc work, right? So it’s a plus?

it depends. it might also come with some more overhead because on every call the var has to be dereferenced. I'm thinking of a couple of optimizations here: - https://github.com/borkdude/sci/issues/483 - add :direct-linking option (or allow this programmatically from within a sci program)

but I think deref-ing a sci var is cheap

will have to do some benchmarks

in CLJS people are used to not having vars at runtime anyway

unless you're in self-hosted

so it's a bit of a grey area

for macros it's not so important, since macros are usually not re-defined

I think I have in fact a couple of macros in sci that aren't vars (just because I didn't bother to make them vars)

in short: doing {:namespaces {'foo (with-meta foo {:sci/macro true})}} is fine

^ @mkvlr

hmm, and this should work from both Clojure + ClojureScript?

trying…

yes

(defn make-sci-namespace [ns-name]
  (into {} (map (fn [[var-name the-var]]
                  (println var-name)
                  [var-name (cond-> @the-var
                              (-> the-var meta :macro)
                              (with-meta {:sci/macro true}))])) (ns-publics ns-name)))

trying this approach now…

but getting stuck on let-coordinates which is imported https://github.com/sicmutils/sicmutils/blob/master/src/sicmutils/env.cljc#L346

ok, but this should work where it’s defined and then just copy it over

indeed there it does work

ok, 💯 I think I’m good

@borkdude I have all my sci namespaces as a map now, but trouble calling my macro. It works from Clojure but not from ClojureScript…

can you repro this?

if you want I can also do a short video call now

oh yes please

ok just a minute