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1 point by jazzdev 5305 days ago | link | parent

I'm not (terribly) surprised that the ability to modify literals was intentional. Thanks for that link. I'm still wondering if `(1) expanding to '(1) is intentional or not.

Clearly '(foo) is a literal and `(foo ,bar) is not a literal, right? I guess it's not a huge stretch to say that `(foo) is a literal. Unfortunately, qq-expand doesn't always expand `(...) with no commas into '(...)

  Jarc> (qq-expand '(foo))
  (quote (foo))  ; literal
  Jarc> (qq-expand '(foo bar))
  (quote (foo bar)) ; literal
  Jarc> (qq-expand '(foo nil))
  (list (quote foo) nil) ; not a literal
But Arc does expand `(foo nil) into a literal

  arc> (def foo(s) (let a `(3 nil) (= (car a) (cons s (car a)))))
  #<procedure: foo>
  arc> (foo 2)
  (2 . 3)
  arc> (foo 1)
  (1 2 . 3)


2 points by aw 5304 days ago | link

I'm still wondering if `(1) expanding to '(1) is intentional or not.

A quasiquote expander can expand `(1) into '(1) or (list 1), or even (join '(1) ' nil), which is what Bawden's simple, correct, but inefficient quasiquote expander does.

The expander may choose '(1) as being more efficient than (list 1), but isn't required to do so to be a quasiquote expander.

Since it's an optimization, I wouldn't write code that relies on a particular instance of `(1) evaluating to the same list every time, that's just an accidental result of the optimization. Instead, use a plain quote for that.

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1 point by fallintothis 5305 days ago | link

That's a bug. It didn't think that nil was a constant. Apparently I didn't know about literal 327 days ago. Thanks for finding it. :)

http://bitbucket.org/fallintothis/qq/changeset/6c0dab5f091e

(Really, all of that code needs a good rewrite. It was straight-ported from some Common Lisp, and suffers greatly for it. Bleh.)

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3 points by fallintothis 5304 days ago | link

There. Just updated qq.arc, removing almost 100 lines of cruft in the process. It still passes all the old tests, and (with any luck) is much more pleasant to work with.

http://bitbucket.org/fallintothis/qq/src/tip/qq.arc

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2 points by aw 5304 days ago | link

Yay!

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