# [racket] on the arity of the composition of procedures with different arities

After looking at collects/racket/private/list.rkt, I think this issue
might be too hard to deal with; I forgot that a procedure could have
optional and keyword arguments.
Thus, I decided to roll my own stripped-down version of 'compose'; I
only need a little of it actually.
Thank you.
On Tue, 2012-08-07 at 22:56 -0500, Robby Findler wrote:
>* Looks like a bug in compose1 (and compose) to me.
*>*
*>* Robby
*>*
*>* On Tue, Aug 7, 2012 at 10:46 PM, Erik Dominikus
*>* <erik.dominikus71 at gmail.com> wrote:
*>* > I had this conversation with DrRacket 5.2:
*>* >
*>* >> (procedure-arity (compose1 (lambda (x) 0) (lambda () 0)))
*>* > (arity-at-least 0)
*>* >
*>* >> (procedure-arity (compose1 (lambda (x) 0) (lambda (x) 0)))
*>* > 1
*>* >
*>* >> (procedure-arity (compose1 (lambda (x) x) (lambda (x y) 0)))
*>* > (arity-at-least 0)
*>* >
*>* > I think the arity of the first procedure above should be exactly 0 since
*>* > (arity-at-least 0) means that the procedure can take 0, 1, 2, 3
*>* > arguments and so on, and indeed DrRacket says that it can't:
*>* >
*>* >> ((compose1 (lambda (x) 0) (lambda () 0)) 0)
*>* > #<procedure>: expects no arguments, given 1: 0
*>* >
*>* > By the same way of thought, I think the arity of the third procedure
*>* > should be exactly 2.
*>* >
*>* > Am I missing something?
*>* >
*>* > ____________________
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*>* > http://lists.racket-lang.org/users
*