10進数と2進数の変換

もちろん書く必要はないのですが、ラフスケッチ的な。

	(define (quotient-down n divider)
	(let loop ((n n)(acc '()))
	(if (zero? n)
	acc
	(loop (quotient n divider)(cons n acc)))))
	(define (number-list->number lis)
	(string->number (string-join (map x->string lis) "")))
	(define (dec->bin n)
	(number-list->number
	(map (lambda (e)
	(if (zero? (remainder e 2)) 0 1))
	(quotient-down n 2))))
	(dec->bin 172)
	(number->string 172 2)
	(dec->bin 60)
	(number->string 60 2)
	(dec->bin 128)
	(number->string 128 2)
	(dec->bin 100)
	(number->string 100 2)
	(define (number->number-list n)
	(map (compose string->number string)
	(string->list (number->string n))))
	(use srfi-1)
	(define (reverse-index-expt ls)
	(unfold null?
	(lambda (s)
	(expt 2 (- (length s) 1)))
	cdr ls))
	(define (bin->dec n)
	(let1 bls (number->number-list n)
	(apply + (filter-map (lambda (b e)
	(and (= b 1) e))
	bls
	(reverse-index-expt bls)))))
	(bin->dec 10011001)
	(bin->dec 1111)
	(bin->dec 1101)
	(bin->dec 1110)

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