SICP 問題 2.40
(define (unique-pairs n) (flatmap (lambda (i) (map (lambda (j) (list i j)) (enumerate-interval 1 (- i 1)))) (enumerate-interval 1 n))) (define (prime-sum-pairs n) (map make-pair-sum (filter prime-sum? (unique-pairs n))))
(define (unique-pairs n) (flatmap (lambda (i) (map (lambda (j) (list i j)) (enumerate-interval 1 (- i 1)))) (enumerate-interval 1 n))) (define (prime-sum-pairs n) (map make-pair-sum (filter prime-sum? (unique-pairs n))))