Arc Forum | "And if that breaks, then you bring out eval" wart> = l '((1 2)) wart>...

Arc Forum

1 point by akkartik 4440 days ago | link | parent

"And if that breaks, then you bring out eval"

  wart> = l '((1 2))
  wart> (and @l) ; error
  wart> (wrap.and @l) ; error
  wart> (eval `(,wrap.and ,@l)) ; error
  wart> (eval `(,wrap.and ,@(map (fn(_) (cons quote _)) l))) ; error

I think our aesthetics are in disagreement :) When the second one (or maybe the third one, in extreme extremis) fails, I would simply go back and rewrite all-true to not use apply/splice, like I did all: http://github.com/akkartik/wart/commit/d25410707d

1 point by Pauan 4440 days ago | link

Er, shouldn't it be (list quote _) ...? In any case, you can wrap up the last one into a function:

  (def operate (f args)
    (eval `(,f ,@(map (fn (_) (list quote _)) args))))

Then it would just be (operate and l)

I'm not saying that's necessarily a good idea, but if it comes up often enough, might as well write a helper function for it.

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And when I said "bring out eval" I meant like this:

  (eval `(,and ,@l))

In other words, not wrapping it.

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2 points by akkartik 4440 days ago | link

"In other words, not wrapping it."

Ah, this works :)

  (eval `(,and ,@(map (fn(_) (cons quote _)) l)))

In wart, 'a is just (' . a). That eliminates questions like, "what happens if quote gets multiple args?" :)

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1 point by akkartik 4440 days ago | link

Pauan, I'm starting to think it's a win to define mapquote like you suggested:

  def all-true(xs)
    (and @mapquote.xs)

But using quoting to suppress future eval like this makes me nervous. Do you think it's a correct transformation?

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1 point by Pauan 4439 days ago | link

My position is quite simple: if you want clean elegance, just use Kernel. Seriously.

If that definition of all-true works and doesn't have any noticeable bugs... then go ahead and use it. It'll be hacky and won't be clean and elegant, but it'll be short and simple and work. And it seems to me that wart is trying to get the power of fexprs in a more hacky Arc-ish way, so that's perfectly fine.

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1 point by Pauan 4440 days ago | link

Ah, like PicoLisp. Neat, I like that.

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