在Haskell中，你如何乘以一个字符串列表？ [英] In Haskell how can you multiply a list of string?

问题描述

我试图编写一个函数，该函数接受一个字符串和一个Int列表，并返回每个字符串都是int次的字符串列表。即：

I'm trying to write a function that takes a list of Strings and an Int and returns that list of strings in which every string is "int" times. That is:

duplicate :: [String] -> Int -> [String]
duplicate ["ab","ac","yt","hfg","lkj","poi"] 2 

输出应该是 $ b

the output should be

["ab","ab","ac","ac","yt","yt","hfg","hfg","lkj","lkj","poi","poi"]

推荐答案

duplicate = (. replicate) . (>>=)

或更多基本

or more basic

duplicate xs n = concatMap (replicate n) xs

<如果你想通过表示法进行列表乘法运算，那么你可以使用

if you want to have list multiplication by notation as well

> let (**) :: [a] -> Int -> [a]
|     (**) = (. replicate) . (>>=)

> ["a","b"]**3
["a","a","a","b","b","b"]

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