问题描述
如何比较两个C ++ 11 std :: function s与 operator == ，并返回 true 如果函数都指向相同的函数指针？
How can I compare two C++11 std::functions with operator==, and return true if both of said functions refer to the same function pointer?
推荐答案
为 std :: function 比较一个 std :: function 与一个空指针，就我可以告诉标准不提供任何细节为什么。
operator== for std::function compares a std::function with a null pointer, as far as I can tell the standard does not provide any details as to why.
虽然，这个提升常见问题项目，提供了一个基本原理，据我所知，应该适用于。引用常见问题解答：
Although, this boost FAQ entry, Why can't I compare boost::function objects with operator== or operator!=? provides a rationale and as far as I can tell should be applicable to std::function as well. Quoting the FAQ:
然后概述类似于Preet的请求解决方案，并继续说：
it then outlines requested solutions similar to Preet's and goes on to say:
并解释为什么必须在赋值运算符或构造函数中处理，然后继续说：
and explains why this has to has to be dealt with in either the assignment operator or constructor and then goes on to say:
更新
在，它很漂亮，但与boost常见问题一致，并说：
Found a standards rationale in Accessing the target of a tr1::function object, which is pretty old but is consistent with the boost FAQ and says:
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