2022-08-28 meander | Clojure Slack Archive

meander 2022-08-28

timothypratley 2022-08-28T19:54:01.622639Z

(s/rewrite 1 2 ?x (m/cata 1))
Syntax error macroexpanding meander.substitute.epsilon/substitute at (/private/var/folders/8r/y2d3thln6s3fyrl_s6vknb440000gn/T/form-init7105795044570115737.clj:1:1).
cata not allowed here
(m/rewrite :a 1 2 ?x (m/cata 1))
=> 2

^^ This is confusing to me 🙂

noprompt 2022-08-29T21:19:31.004769Z

Is s/rewrite expanding incorrectly?

noprompt 2022-08-29T21:20:09.086709Z

I think that error is when m/cata is on the left side, top level.

noprompt 2022-08-29T21:20:21.407339Z

Expansion might be the issue

timothypratley 2022-08-29T21:22:26.578559Z

no big deal, I wouldn't worry about it, just reported it. ¯\(ツ)/¯

timothypratley 2022-08-29T21:22:46.405819Z

one thing I was wondering was whether meander does or can do tail recursion

timothypratley 2022-08-29T21:23:00.675539Z

I was messing with using m/app recur

timothypratley 2022-08-29T21:23:13.976149Z

and it kinda almost does something but complains about the number of args

timothypratley 2022-08-29T21:23:20.023049Z

probably due to function nesting

timothypratley 2022-08-29T21:23:25.986129Z

lol I have no idea what I'm talking about

timothypratley 2022-08-29T21:23:55.380539Z

I was doing some reasonably weird stuff admittedly.

timothypratley 2022-08-29T21:25:49.012819Z

But it seemed to work fine with m/rewrite so that's good 🙂

timothypratley 2022-08-29T21:32:13.537779Z

To answer you question directly:

(macroexpand '(s/rewrite 1 2 ?x (m/cata 1)))
=>
(fn*
 ([x__7086__auto__]
  (meander.match.epsilon/find
   x__7086__auto__
   1
   (meander.substitute.epsilon/substitute 2)
   ?x
   (meander.substitute.epsilon/substitute (m/cata 1))
   _
   meander.strategy.epsilon/*fail*)))

and the other one:

(macroexpand '(m/rewrite :a 1 2 ?x (m/cata 1)))
=>
(let*
 [TARGET__8094 :a]
 (clojure.core/let
  [R__8099
   (clojure.core/letfn
    [(C__8092
      [TARGET__8094]
      (clojure.core/letfn
       [(state__8096 [] (if (clojure.core/= TARGET__8094 1) [2] (state__8097)))
        (state__8097
         []
         (clojure.core/let
          [?x TARGET__8094]
          (try
           [(clojure.core/let
             [R__8093 (C__8092 1)]
             (if
              (meander.match.runtime.epsilon/fail? R__8093)
              (throw meander.substitute.runtime.epsilon/FAIL)
              (clojure.core/nth R__8093 0)))]
           (catch
            clojure.lang.ExceptionInfo
            e__6502__auto__
            (if
             (meander.substitute.runtime.epsilon/fail? e__6502__auto__)
             meander.match.runtime.epsilon/FAIL
             (throw e__6502__auto__))))))]
       (state__8096)))]
    (clojure.core/let
     [R__8098 (C__8092 TARGET__8094)]
     (if
      (meander.match.runtime.epsilon/fail? R__8098)
      meander.match.runtime.epsilon/FAIL
      (clojure.core/let [[R__8095] R__8098] R__8095))))]
  (if (meander.match.runtime.epsilon/fail? R__8099) nil R__8099)))

timothypratley 2022-08-29T21:32:36.014289Z

¯\(ツ)/¯

timothypratley 2022-08-29T21:33:03.776059Z

I think just ignore it for now.

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meander 2022-08-28