On Aug 23, 2014, at 10:03 PM, Kevin Forchione <[email protected]> wrote:
> I’ve been trying to figure out the syntax for optional keywords in the ->i
> contract form. For example:
>
> (->i ([lst list?])
> ([#:foo ….]) ; what does this look like?
> (result list?))
>
> The mandatory domain syntax seems straightforward, but I’ve tried various
> combinations for the optional keyword that don’t appear to be correct.
>
> (->i ([lst list?])
> ([#:foo (lst) (….etc)))
> (result list?))
>
> doesn’t work for me, neither does sticking an id before or after … (lat) …
>
> Does anyone have an example of an optional keyword ->i contract? This would
> seem to be an extremely useful form, but the examples in the documentation do
> not appear to cover it. They do cover the ->* form, but not the ->i for that
> combination.
Well, I seem to have sussed it. But I find it odd that the contract doesn’t
appear to apply to the optional value as supplied. For example, the below shows
a sample of ->*, and an ->i version that shows points up the issue:
#lang racket
(define/contract (foo x #:y y #:z (z 42))
(->* (integer?
#:y integer?)
(#:z integer?)
list?)
(list x y z))
(foo 3 #:y 1)
(define/contract (bar x #:y y #:z (z 42))
(->i ([x integer?]
#:y (y integer?))
(#:z (z (x y) (integer-in x y)))
(result list?))
(list x y z))
(bar 3 #:y 5)
(bar 3 #:y 5 #:z 4)
-Kevin____________________
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