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1 point by rocketnia 3240 days ago | link | parent

Hmm, I wonder if each is a good way to encode the lazy-list conversion. Perhaps it makes sense to make each generic, and map just use each.

Feels a bit like you missed my point. Just in case, it was:

1. Make 'some, 'fn-ifdecap, and 'as-lazy-list generic.

  ; 'defgeneric versions
  (some (fn (x) <test>) xs)
  (fn-ifdecap (fn (x xs) <split case>) (fn () <empty case>) xs)
  (as-lazy-list (fn (lazy-orig) <lazy result>) orig)
  
  ; the versions I currently have in my Penknife core library draft
  [fn-any xs [fn [x] <test>]]
  [fn-ifdecap xs [fn [x xs] <split case>] [fn [] <empty case>]]
  [fn-decap-erism orig [fn [lazy-orig] <lazy result>]]
    ; I'll probably rename this to "call-as-seq".
    ; A "decap-er" is something that has fn-ifdecap behavior.
2. Base utilities like 'ifdecap (a macro), 'all, 'each, and 'map off of these.

The version of 'map in my draft is something like this:

  [fun fn-map [seq func]
    [rely:decap-erism lazy-seq seq
      [nextlet rest lazy-seq  ; aka xloop, or named let
        [make-decap-er:fn [then else]
          [ifdecap first rest rest
            [then func.first next.rest]
            else.]]]]]
No 'each is required, just 'fn and 'xloop. :) And the 'xloop is just there to keep from bothering with conversion when recurring on the tail.

Aside: The "rely" here is supposed to make the result of fn-map undefined if the result of decap-erism is undefined. That part probably isn't easy to translate to Arc; I essentially have an extra implicit parameter in every Penknife function call, specifying what to try instead if the call is rejected. It's kind of a tacked-on thing, and I'd avoid it if I had some better idea, but it seems to help immensely with writing extensible utilities.