nothingrealhappen/甘大大出的题目

Created March 31, 2015 10:51

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20150331「每日一题」怕了么？

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甘大大出的题目

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nothingrealhappen commented Mar 31, 2015

使用 lisp 或 js 写一个 stream

注: 永远返回一个 pair, (car (s)) 返回一个数, (cdr (s))则返回下一个 stream,
(car ((cdr (s))) 会返回第二个数, 可以无限的取下去.

写一个 stream 叫 funny-number-stream 
每次返回的是自然数(例 1, 2, 3, ...)
每到一个可以被5整除的数则变为负数(例: 1, 2, 3, 4, -5, 6, 7, 8, 9, -10, 11, ...)
注意: stream 是一个 thunk, 每次被 call 会产生一个 pair, car 是数字, cdr 是另外一个 stream

flypiggy commented Mar 31, 2015

(= (car (funny-number-stream)) 1)
(= (car ((cdr (funny-number-stream)))) 2)

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