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3dcgmodeling

mapchar*,T*,CompareTwoStrings and const

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class CompareTwoStrings { public: bool operator()(char* a, char* b) const // must add the const { if(strcmp(a,b) < 0) return true; else return false; } }; std::map<char*,T*,CompareTwoStrings> font_map; if you do not put const after operator(),it will raise compiler error. why I need to add the const? what i know is: if you set map<const char*,T*,CompareTwoStrings> then you need make operator() const .

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well, it seems the map requires that you do not change anything when you call the compare object. Think about it: if you were to change the object in that comparison routine, then the order of the map would change. The only way the compiler can prove that you don't change anything is if the method is const. And it also points out the above information if you do not.

Compiler: You cannot change the data without screwing things up

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