Eduardo Cavazos wrote:
>> I'd like for it to just be:
>>
>> (define (queue-empty? (record queue L R P))
>> (and (stream-null? L)
>> (stream-null? R)
>> (stream-null? P)))
>>
>> I.e. let 'define' do the deconstructing for me.
Tristan Ravitch wrote:
I don't quite have a destructuring define, but I did make a
destructuring bind macro. You can check it out here:
http://pages.cs.wisc.edu/~travitch/cynara.tar.gz
Eduardo Cavazos wrote:
Wow, this is very nice! I'm glad I asked! Thanks!
queue-empty? using bind is:
(define (queue-empty?* q)
(bind (((&record L R P) q))
(and (stream-null? L)
(stream-null? R)
(stream-null? P))))
Going further, and building on Tristan's 'bind', it's possible to have a
macro that allows for the first syntax I hinted at. Here's a working
definition of queue-empty? :
(def (queue-empty? (&record L R P))
(and (stream-null? L)
(stream-null? R)
(stream-null? P)))
Another example; a procedure that reverses a two element list:
(def (swap (&list a b))
(list b a))
'def' is:
(import (cynara bind))
(define-syntax def
(lambda (stx)
(syntax-case stx ()
((def (f p ...) body ...)
(with-syntax (((x ...) (generate-temporaries (syntax (p ...)))))
(syntax
(define (f x ...)
(bind ((p x) ...)
body
...))))))))
Ed
