带有 lambda 比较器错误的 C++ priority_queue-C/C++问题

C++ priority_queue with lambda comparator error(带有 lambda 比较器错误的 C++ priority_queue)

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问题描述

我尝试在 VC2010 中编译以下错误代码，但出现错误 C2974 这只发生在我包含 lambda 表达式时，所以我猜它与此有关.

typedef pair, int>adjlist_edge;优先队列，[](adjlist_edge a, adjlist_edge b) ->布尔{if(a.second > b.second){ 返回真；} else { 返回假；}}>adjlist_pq;

我知道模板定义的形式是正确的

priority_queue、greater>pq;

按预期工作.任何想法我做错了什么?lambda 是否有明显的错误，看起来我可能忽略了?感谢阅读！

解决方案

首先定义 lambda 对象，然后使用 decltype 将其传递给模板的类型，并直接将其传递给构造函数.

auto comp = []( adjist a, adjlist b ) { return a.second >b.第二；};优先队列，decltype(comp)>adjlist_pq(comp);

I have the following erroneous code which I am trying to compile in VC2010, but I'm getting the error C2974 this only occurs when I include the lambda expression, so I'm guessing it has something to do with that.

typedef pair<pair<int, int>, int> adjlist_edge;
priority_queue< adjlist_edge , vector<adjlist_edge>,
    [](adjlist_edge a, adjlist_edge b) -> bool {
        if(a.second > b.second){ return true; } else { return false; }
    }> adjlist_pq;

I know the form of the template definition is correct as

priority_queue<int , vector<int>, greater<int>> pq;

Works as expected. Any ideas what I'm doing wrong? Is there something obviously wrong with the lambda that looks wrong that I might be overlooking? Thanks for reading!

解决方案

First define the lambda object, then pass it to the template's type using decltype and also pass it directly to the constructor.

auto comp = []( adjist a, adjlist b ) { return a.second > b.second; };
priority_queue< adjlist_edge , vector<adjlist_edge>, decltype( comp ) >
     adjlist_pq( comp );

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