#;31> (define rec itrec)
#;32> ((rec zero? 1 * sub1) 6)
Error: during expansion of (letrec ...) - (letrec) unexpected object:
((zero? 1 * sub1))
#;32> (eq? rec itrec)
#t
#;33> ((rec zero? 1 * sub1) 6)
Error: during expansion of (letrec ...) - (letrec) unexpected object:
((zero? 1 * sub1))
#;33> ((itrec zero? 1 * sub1) 6)
720
#;34>
itrec and rec are the same, but one makes error and the other doesn't.
csi -version
Version 2, Build 214 - linux-unix-gnu-unknown - [ dload ptables ]
Chicken and csi is from darcs repo a couple of days ago.
; This is the definition of itrec
(define (itrec break start do inc)
(lambda (x)
(let loop ((x x) (total start))
(if (break x)
total
(loop (inc x) (do x total))))))
;; and this is the definition of rec that I originally wanted to have,
;; but the behaviour is as crazy regardless of what rec does.
;; even with (define rec itrec) it becomes crazy!
;; or with (define rec list) or define rec anything, anything!
(define (rec break fin do inc)
(lambda (x)
(let loop ((x x))
(if (break x)
fin
(do x (loop (inc x)))))))
I wanted to make an implementation of the idea in near the bottom of
http://www.paulgraham.com/power.html
help!
years truely,
sunnan
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