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As an alternative to your 'rec', there's the fixed-point-finding function
'call-with-result' that I implemented in my Scheme interpreter HScheme.
call-with-result calls a function, passing to it the result that the
function will return. For instance:
(define factorial (call-with-result (lambda (fact)
(lambda (x)
(if (equal? x 0) 1 (* x (fact (- x 1))))
)
)))
(define stream1 (call-with-result (lambda (s)
(cons 1 s)
)))
It's a little time-travel trick. You can try it out here:
<http://hscheme.sourceforge.net/examples.html>
Unfortunately call-with-result seems to be incompatible with CPS (and
apparently therefore with call-with-current-continuation), so the
resulting Scheme isn't R5RS. HScheme comes in both flavours, but is not
yet R5RS-complete for other reasons.
--
Ashley Yakeley, Seattle WA