重寫過(guò)程中,發(fā)現(xiàn)這種做法能加深對(duì)遞歸的理解,而且reduce還體現(xiàn)了函數(shù)式編程是如何通過(guò)參數(shù)傳遞來(lái)實(shí)現(xiàn)命令式編程中的狀態(tài)改變的.

(define (imap f x . y)(if (null? y) (let recur ((x x)) (if (null? x) '() (cons (f (car x)) (recur (cdr x))))) (let recur ((x x) (y y)) (if (null? x) '() (cons (apply f (car x) (imap car y)) (recur (cdr x) (imap cdr y)))))))(map + '(1 2 3) '(1 2 3) '(1 2 3)) (imap + '(1 2 3) '(1 2 3) '(1 2 3)) (define (filter f x)(let recur ((x x))(if (null? x)'()(if (f (car x))(cons (car x) (recur (cdr x)))(recur (cdr x))))))(filter even? '(1 2 3 4 5)) (define (reduce f x . ini)(if (null? ini)(let recur ((res (f (car x) (cadr x)))(x (cddr x)))(if (null? x)res(recur (f res (car x)) (cdr x))))(reduce f (cons (car ini) x))))(reduce + '(1 2 3 4)) (reduce + '(1 2 3 4) 10) (reduce * '(1 2 3 4)) (reduce * '(1 2 3 4) 10)

?

結(jié)果:

(3 6 9) (3 6 9) (2 4) 10 20 24 240 >

?

轉(zhuǎn)載于:https://www.cnblogs.com/xiangnan/p/3391437.html

總結(jié)

以上是生活随笔為你收集整理的用scheme重写Python的三大函数map reduce 和filter的全部?jī)?nèi)容，希望文章能夠幫你解決所遇到的問(wèn)題。

如果覺(jué)得生活随笔網(wǎng)站內(nèi)容還不錯(cuò)，歡迎將生活随笔推薦給好友。