如何在C ++中制作无序的整数对对? [英] How can I make an unordered set of pairs of integers in C++?
问题描述
以下程序不会编译整数对的无序集合,但是会编译整数。 unordered_set
及其成员函数可以用于用户定义的类型,如何定义它?
The following program does not compile an unordered set of pairs of integers, but it does for integers. Can unordered_set
and its member functions be used on user-defined types, and how can I define it?
#include <unordered_set>
...
class A{
...
private:
std::unordered_set< std::pair<int, int> > u_edge_;
};
编译器错误:
错误:没有匹配函数调用'std :: unordered_set> :: unordered_set()'
error: no matching function for call to 'std::unordered_set >::unordered_set()'
推荐答案
您的代码可以在VS2010 SP1(VC10)上编译,但是无法在GCC g ++ 4.7.2上编译。
Your code compiles on VS2010 SP1 (VC10), but it fails to compile with GCC g++ 4.7.2.
但是,您可能想要考虑从 Boost进行的 boost :: hash
.Functional 散列 std :: pair
(加上此代码,您的代码也可以使用g ++进行编译)。
However, you may want to consider boost::hash
from Boost.Functional to hash a std::pair
(with this addition, your code compiles also with g++).
#include <unordered_set>
#include <boost/functional/hash.hpp>
class A
{
private:
std::unordered_set<
std::pair<int, int>,
boost::hash< std::pair<int, int> >
> u_edge_;
};
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