At Sun, 4 Mar 2012 20:36:23 -0800,
Helmut Rohrbacher wrote:
> The only thing is, how do you extend these properties to built-in types
> like LIST and VECTOR? I'm guessing that you'd need to wrap them in a
> user-defined type...
You could do that, or you could handle them specially in your generic
function. Using Danny's example:
(define (doolittle! entity)
(cond
[(list? entity)
(printf "Lists don't speak.")]
[(prop:speak? entity)
(printf "~a says: " entity)
((prop:speak-ref entity) entity)]
[else
(raise-type-error 'speak! "speaking animal" entity)]))
Vincent
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