XPost: comp.lang.scheme

Lars Brinkhoff wrote:

use LOOP to collect random integers into a list until the sum of that
list exceeds a constant (say 50).

(loop for x = (random 10) collect x sum x into y until (> y 50))

Let's see if it's shorter in Gauche Scheme.

(loop (y) (:coll (++. y (random 10))) (:till (> y 50)))

Yes, it is.

Given:

(use srfi-27) ;; random-integer
(define random random-integer)

;; Returns the added number, not the sum.
(define-syntax ++.
(syntax-rules ()
[(++. place val)
(let ((x val)) (set! place (+ x place)) x)]
[(++. place) (++. place 1)]))

I don't want to include the rather lengthy source for
"loop" here, so defining it is left as an exercise for
the reader.

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XPost: comp.lang.scheme

Lars Brinkhoff wrote:

use LOOP to collect random integers into a list until the sum of that
list exceeds a constant (say 50).

(loop for x = (random 10) collect x sum x into y until (> y 50))

Gauche Scheme

(let1 y 0 (collect-till x (random 10) (> (inc! y x) 50)))
===>
(7 9 4 0 6 4 1 3 2 7 0 7 0 1)


Given:

(use srfi-27) ;; random-integer

(define random random-integer)

(define-syntax collect-till
(syntax-rules ()
[(collect-till v expr0 expr1)
(let ((res '()))
(let go ((v expr0))
(set! res (cons v res))
(if expr1 (reverse res) (go expr0))))]))

(collect-till x (random 10) (even? x))
===>
(7 1 6)

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XPost: comp.lang.scheme

B. Pym wrote:

Lars Brinkhoff wrote:

use LOOP to collect random integers into a list until the sum of that list exceeds a constant (say 50).

(loop for x = (random 10) collect x sum x into y until (> y 50))

Gauche Scheme

(let1 y 0 (collect-till x (random 10) (> (inc! y x) 50)))
===>
(7 9 4 0 6 4 1 3 2 7 0 7 0 1)

Given:

(use srfi-27) ;; random-integer

(define random random-integer)

(define-syntax collect-till
(syntax-rules ()
[(collect-till v expr0 expr1)
(let ((res '()))
(let go ((v expr0))
(set! res (cons v res))
(if expr1 (reverse res) (go expr0))))]))

(collect-till x (random 10) (even? x))
===>
(7 1 6)

Revision:

(collect-till (x (y 0)) (random 10) x (> (inc! y x) 50))

Given:

(define-syntax collect-till
(syntax-rules ()
[(collect-till (v (w x) ...) v-val collect test)
(let ((res '()) (w x) ...)
(let go ((v v-val))
(set! res (cons collect res))
(if test (reverse res) (go v-val))))]
[(collect-till v v-val collect test)
(collect-till (v) v-val collect test)]))

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