提高:: ::的UUID UUID作为中的std :: unordered_map的关键？ [英] boost::uuids::uuid as a key in std::unordered_map?

问题描述

我使用铛（CXX ='铛++ -std = C ++ 11 -stdlib = libc中++'）在Mac OS X，与升压1.53.0。

I'm using clang (CXX='clang++ -std=c++11 -stdlib=libc++') on Mac OS X, with boost 1.53.0.

我想用UUID作为unordered_map键，但得到以下错误：

I want to use uuid as keys in unordered_map, but getting the following errors:

/usr/bin/../lib/c++/v1/type_traits:748:38: error: implicit instantiation of undefined template
      'std::__1::hash<boost::uuids::uuid>'
    : public integral_constant<bool, __is_empty(_Tp)> {};
                                 ^
/usr/bin/../lib/c++/v1/unordered_map:327:54: note: in instantiation of template class
      'std::__1::is_empty<std::__1::hash<boost::uuids::uuid> >' requested here
template <class _Key, class _Tp, class _Hash, bool = is_empty<_Hash>::value

...

/usr/bin/../lib/c++/v1/unordered_map:327:71: error: no member named 'value' in
      'std::__1::is_empty<std::__1::hash<boost::uuids::uuid> >'
template <class _Key, class _Tp, class _Hash, bool = is_empty<_Hash>::value
                                                     ~~~~~~~~~~~~~~~~~^

...

这是什么 - 升压中的一个错误，这使得它与我的C ++的lib不兼容？还是我做错了什么？任何变通办法？

What is it - a bug in Boost, which makes it incompatible with my C++ lib? Or I am doing something wrong? Any workarounds?

推荐答案

为什么错误的提升？你应该专注的std ::对升压哈希模板:: UUID 。

Why bug in boost? You should specialize std::hash template for boost::uuid.

#include <boost/functional/hash.hpp>

namespace std
{

template<>
struct hash<boost::uuids::uuid>
{
    size_t operator () (const boost::uuids::uuid& uid)
    {
        return boost::hash<boost::uuids::uuid>()(uid);
    }
};

}

，或简单地创建 unordered_map 与的boost ::哈希参数

std::unordered_map<boost::uuids::uuid, T, boost::hash<boost::uuids::uuid>>

或提供散仿函数满足的std ::哈希（感谢执政官）的要求。

or provide hash functor that satisfies requirements of std::hash (thanks to Praetorian).

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