On 05/14/2011 08:55 PM, Kazimir Majorinc wrote:
I want to write the function "counted" that generates closures in
Scheme; I want that after this
(define f (counted '(x) '(+ x x)))
f behaves like I wrote
(define f (let((i 0))
(lambda(x) ;first argument
(set! i (+ i 1))
(display i)
(+ x x)))) ;second argument
and to avoid symbols leaking which happens if I call
(define f (counted '(i) '(+ i i)))
How would you do that "idiomatically"?
Idiomatically, one would do this instead:
(define (counted proc)
(let ([i 0])
(lambda args
(set! i (+ i 1))
(display i)
(apply proc args))))
(define f (counted (lambda (x) (+ x x))))
because symbols and lists do not adequately represent pieces of Racket
programs. (See also Eli's macro solution.)
Ryan
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