Arc Forum | An extra hash argument can implement both optional and named args. Representing ...

Arc Forum

2 points by binx 6111 days ago | link | parent

An extra hash argument can implement both optional and named args. Representing optional args as varargs would complicate the source transformation when they are used simultaneously in the same function.

2 points by almkglor 6111 days ago | link

Not really:

  (fn (niaw (o hmm) . rest)
    (body niaw hmm rest))

  =>

  (fn (niaw . gs42)
    (with (hmm (if gs42 (car gs42) nil)
           gs42 (cdr gs42))
      (let rest gs42
        (body niaw hmm rest))))

It's not at all complicated: just make the last argument take the value of your temporary rest argument. Edit: This is what I did in creating the p-m macro, and it works.

I'm not sure how adding an extra hash would work well if I might pass several different functions, with different optarg names:

  (set p1
    (fn (hmm (o niaw))
      (body hmm niaw)))
  (set p2
    (fn (hmm (o arf))
      (body hmm arf)))
  (set p3
    (fn rest
      (body rest)))
  ((if (something)
       p1
     (something-else)
       p2
       p3)
  1 42)

Edit: My approach appears to be somewhat similar to what pg did in the Scheme version - cref ac-fn, ac-complex-fn, ac-complex-args, ac-complex-opt in ac.scm

Since code is spec (grumble) I think it might be better to follow mostly what pg did, although I dunno, not sure ^^. How can passing in a hash table seamlessly emulate the same functionality while improving performance?

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