filter-break

リストlisと述語手続きpredを取り、lisの各要素に順にpredを適用して、 predが真の値を返したら直ちにその要素を返すような関数find

	; filter-break
	(define (filter-break pred? ls)
	(if (null? ls)
	#f
	(if (pred? (car ls))
	(car ls)
	(filter-break pred? (cdr ls)))))
	(filter-break odd? '(2 2 2 3 4 4 4))
	; -> 3
	(define (filter-break pred? ls)
	(let/cc skip
	(fold (lambda (e r)
	(if (pred? e)
	(skip e)
	r))
	#f ls)))
	(filter-break odd? '(2 2 2 3 4 4 4))
	; -> 3

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