[racket] About genericity...

From: Patrick Useldinger (uselpa.list at gmail.com)
Date: Fri Apr 4 18:45:50 EDT 2014

On 05/04/2014 00:08, Patrick Useldinger wrote:
> I copied Common Lisp's model, but it's a good idea to add Racket-style
> contracts. It should be a matter of simply adding a matcher for this.

I've pushed a quick fix. Your code becomes:

(def-multi P contract-match-parms)
(add-multi P (listof number?) (lambda args (apply + args)))
(add-multi P (listof vector?) (lambda args (apply v+ args)))

(check-equal? (P 1 2 3) 6)
(check-equal? (P (vector 1 2 3) (vector 2 3 4)) (vector 3 5 7))

I dropped the default method you created ((add-multi + '() (lambda () 
0)) ) because I don't see why you'd need it for, and it prevents proper 
error messages in case no method matches.


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