c++ - 具有类型 'const CompareVPtrs' 的表达式将丢失一些 const-volatile 限定符以便调用

Question

我正在用 C++ 实现十五个益智控制台游戏，引发了以下错误

Error 4  error C3848: expression having type 'const CompareVPtrs' would lose some
   const-volatile qualifiers in order to call 
   'bool CompareVPtrs::operator ()(Vertex *,Vertex *)'    
   c:\program files\microsoft visual studio 11.0\vc\include\xfunctional   
  324 1  puzzle15

这是我的结构

struct CompareVPtrs: public binary_function<Vertex*, Vertex*, bool>
{
    bool operator()( Vertex *lhs, Vertex *rhs)
    {
        return equal((int *)lhs->state, (int *)lhs->state+16,
            (int *)rhs->state);
    }
}
CompareVP;

完整的游戏源代码https://gist.github.com/sunloverz/7338003

Answer 1

这意味着您的比较运算符需要是const:

bool operator()( Vertex *lhs, Vertex *rhs) const
{ //                                       ^^^^^
  ....
}