有什么区别：while和：when in clojure？ [英] What is the difference between :while and :when in clojure?

问题描述

我正在研究clojure，但不太清楚：while 和之间的区别：

I'm studying clojure but not quite clear on the difference between the :while and :when test:

=> (for [x [1 2 3] y [1 2 3] :while (= (mod x y) 0)] [x y])
([1 1] [2 1] [2 2] [3 1])
=> (for [x [1 2 3] y [1 2 3] :when (= (mod x y) 0)] [x y])
([1 1] [2 1] [2 2] [3 1] [3 3])

任何人都可以通过阐述来帮助他们？

Can anybody help by elaborating on them ?

推荐答案

：当迭代绑定时，当条件为真时。 ：while 遍历绑定并评估正文，直到条件为假：

:when iterates over the bindings, but only evaluates the body of the loop when the condition is true. :while iterates over the bindings and evaluates the body until the condition is false:

(for [x (range 20) :when (not= x 10)] x)
; =>(0 1 2 3 4 5 6 7 8 9 11 12 13 14 15 16 17 18 19)

(for [x (range 20) :while (not= x 10)] x)
; => (0 1 2 3 4 5 6 7 8 9)

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