对于Enumerable.Intersperse扩展方法？ [英] Extension method for Enumerable.Intersperse?

问题描述

我学到了点缀功能< 。/ A>从哈斯克尔，并一直在寻找在C＃中实施

I learned the intersperse function from Haskell, and have been looking for an implementation in c#.

中散布需要两个参数，一个IEnumerable< T>源和T元件。它返回一个IEnumerable与源中的每个元素之间插入的元素

Intersperse takes 2 arguments, an IEnumerable<T> source and a T element. It returns an IEnumerable with element inserted between every element of source.

一个可能的用例是把一个任意整数整数列表之间，例如：

One possible use-case is to put an arbitrary integer in between a list of integers, for example:

// returns: {1, 0, 2, 0, 3}
(List<int>() {1, 2, 3}).Intersperse(0);

这是的string.join（...）的一般情况。

This is a general case of string.Join(...).

推荐答案

东西别人已经错过：如果你只希望它在项目之间，不也是在前面还是后面，你需要做额外的检查：

Something the others have missed: if you only want it in between items, and not also in front or behind, you need to do an extra check:

public static IEnumerable<T> Intersperse<T>(this IEnumerable<T> source, T element)
{
    bool first = true;
    foreach (T value in source)
    {
        if (!first) yield return element;
        yield return value;
        first = false;
    }
}

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