On Tue, Aug 7, 2012 at 10:46 PM, Erik Dominikus
<erik.dominiku...@gmail.com> wrote:
> I had this conversation with DrRacket 5.2:
> [...]
On August 7th, Robby Findler wrote:
> Looks like a bug in compose1 (and compose) to me.
The source of both `compose' and `compose1' has the place where this
would be fixed -- see the "here" below:
[(composed)
;; FIXME: would be nice to use `procedure-rename',
;; `procedure-reduce-arity' and `procedure-reduce-keyword-arity'
;; in the places marked below, but they currently add a
;; significant overhead.
(if (eq? 1 arity)
(lambda (x) (app f (g x)))
(case-lambda ; <--- here
[(x) (app f (g x))]
[(x y) (app f (g x y))]
[args (app f (apply g args))]))]
The reason I chose to avoid the overhead for getting a precise arity
is that I think that people expect function composition to be pretty
fast. TBH, I'd even go to the point of defining it as a macro so that
simple uses like ((compose1 f g) X) expand to an explicit `lambda'
which would then be optimized away.
(This is also re PR 13003, which resulted from the above; CCed bugs.)
--
((lambda (x) (x x)) (lambda (x) (x x))) Eli Barzilay:
http://barzilay.org/ Maze is Life!
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