过程中的每对的序列 [英] Process every pair in a sequence

问题描述

我在找一个简洁的方式来处理每一个（无序）对元素在.NET中的序列。 我知道我可以嵌套为循环做到这一点，但我一直在寻找的东西多一点可读性。

我想象像一个修改任何（）扩展方法：

 的IEnumerable＆LT;交易＆GT;交易= ...
如果（transactions.AnyPair（（一，二）=＆GT; first.UniqueID == second.UniqueID））
    扔 ...
 

或者，也许一个的foreach 风格之一：

 的IEnumerable＆LT; JigsawPiece＆GT;件= ...
pieces.ForEachPair（（一，二）=＆GT; {
    TryFit（一，二）;
}）;
 

这个问题已经被问了其他语言（如见<一href="http://stackoverflow.com/questions/942543/operation-on-every-pair-of-element-in-a-list">http://stackoverflow.com/questions/942543/operation-on-every-pair-of-element-in-a-list),但我正在寻找一个.NET解决方案。

解决方案

  VAR的查询=交易
             .SelectMany（（VAL1，J）=＆GT; transactions.Select（（val2中，I）=＆gt;新建{V1 = VAL1，V2 = val2中，I = I，当J = J}））
             。凡（X =＆GT; x.i＆LT; x.j）;

VAR的结果= query.Select（X =＆GT; x.v1.UniqueID == x.v2.UniqueID）;
 

该执行的比较正确的次数。结果还包括索引匹配两种元素的I，J。

I'm looking for a concise way to process every (unordered) pair of elements in a sequence in .NET. I know I can do it with nested for loops, but I was looking for something a little more readable.

I was imagining something like a modified Any() extension method:

IEnumerable<Transaction> transactions = ...
if (transactions.AnyPair( (first, second) => first.UniqueID == second.UniqueID))
    throw ...

Or maybe a foreach-style one:

IEnumerable<JigsawPiece> pieces = ...
pieces.ForEachPair( (first, second) => {
    TryFit(first, second);
});

This question has been asked for other languages (e.g. see http://stackoverflow.com/questions/942543/operation-on-every-pair-of-element-in-a-list), but I'm looking for a .NET solution.

解决方案

var query = transactions
             .SelectMany((val1,j) => transactions.Select((val2,i) => new {v1=val1, v2=val2, i=i, j=j}))
             .Where(x => x.i < x.j);

var result = query.Select(x=> x.v1.UniqueID == x.v2.UniqueID);

This performs the comparison the correct number of times. The result also includes the indexes i, j of the two elements that matched.

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