Why cant i use two ptrs in operator overload?

This is annoying, i can write a function with these parameters/return, but why cant i define an operator to do this?

-edit- i am actually trying to overload << the below is just for reference.

From msdn

// C2803.cpp
// compile with: /c
class A{};
bool operator< (const A *left, const A *right);   // C2803
// try t开发者_StackOverflow社区he following line instead
// bool operator< (const A& left, const A& right);

gcc error

error: ‘bool operator<(const A*, const A*)’ must have an argument of class or enumerated type

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Because every user-defined operator overload needs at least one user-defined type as a parameter. A point isn't a user-defined type.

C++03 standard, §13.5 [over.oper] p6:

An operator function shall either be a non-static member function or be a non-member function and have at least one parameter whose type is a class, a reference to a class, an enumeration, or a reference to an enumeration.

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Because you aren't allowed to cheat.

If you could override comparison operators for pointer types, then you would no longer be able to compare those pointers by value (aka: by the actual numerical pointer values). And that's kind of important and occasionally useful.

My real code is actually <<. Why cant i use it for that?

For the same reason: pointers are C++-basic types. They aren't user-defined types. Do you want to be able to not left-shift pointer values anymore? OK, obviously you do, but C++ won't let you.

You can only override operators when C++ does not have existing functionality for operators with those types (with a few exceptions). C++ already has operator< and operator<< for pointers, so you're not allowed to change what they do.