问题描述
我试图为类重载< 运算符，并调用函数如下：
I tried to overload < operator for class and called the function as follows:
bool Edge::operator<(Edge const & e) const {
return this->GetCost() < e.GetCost();
}
在main（）中
sort(edge_set.begin(),edge_set.end());
此外，我还尝试为对象编写一个简单的比较器函数，定义在main.cpp并尝试调用 sort（），但失败了：
In addition, I also tried to write a simple comparator function for the objects, defined in main.cpp and tried to invoke sort(), however failed again:
bool edge_comparator(Edge& e1, Edge& e2){
return (e1.GetCost() < e2.GetCost());
}
在main（）中
sort(edge_set.begin(),edge_set.end(), edge_comparator);
我得到了一个编译错误。我在这里做错了什么？如何排序对象集？
I get a compilation error for those what I tried. What am I doing wrong here? How can I sort the set of objects?
推荐答案
两个问题。首先，你不能重新排序集合的元素。它们的排序标准是在构造时确定的，它是对象的基本部分。这是必要的，以便它实现O（log n）查找，插入和删除，这是 std :: set 的promise的一部分。默认情况下，它将使用 std :: less< Edge> ，它应该调用运算符< 。但您也可以使用 edge_comparator 函数，如下所示：
Two problems. First, you cannot reorder the elements of a set. Their ordering criteria is determined upon construction, it is a fundamental part of the object. This is necessary in order for it to achieve O(log n) lookups, insertions, and deletions, which is part of the promises of std::set. By default, it will use std::less<Edge>, which should call your operator<. But you could also use your edge_comparator function, like this:
std::set<Edge, bool(*)(Edge&,Edge&)> edge_set(edge_comparator);
其次， std :: sort 用于随机访问迭代器或更好， std :: set 迭代器是双向的。
Second, std::sort can only be used on random access iterators or better, and std::set iterators are bi-directional.
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