是否有反向映射函数？ [英] Is there a reverse-map function?

问题描述

在clojure中，您可以将函数映射到值序列。是否有内置函数将单个值映射为函数序列的参数？

In clojure you can map a function to a sequences of values. Is there an inbuilt function to map a single value as parameter to a sequence of functions?

(map inc [1 2 3 4])
; -> (2 3 4 5)

(reverse-map [inc dec str] 1)
; -> (2 0 "1")

(reverse-map [str namespace name] :foo/bar/baz)
; -> (":foo/bar/baz" "foo/bar" "baz")

推荐答案

有 juxt 这有点类似。它需要一些函数，并返回一个将其参数传递给每个函数，并返回一个返回值的向量。所以：

There's juxt which is a bit similar. It takes a number of functions and returns one that passes its argument(s) to each of the functions and returns a vector of return values. So:

> ((apply juxt [inc dec str]) 1)
[2 0 "1"]

主要的区别是它创建了一个向量，当然是热切的（即不是惰性的）。 map 创建一个延迟的序列。

The main difference is that it creates a vector, which is of course eager (i.e. not lazy.) The original map creates a sequence which is lazy.

juxt 也适用于有多个参数的函数：

juxt also works on functions that have more than 1 argument:

> ((apply juxt [* / -]) 6 2)
[12 3 4]

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