Argument-Dependent Lookup

[siddhu]

Dear experts,

As far as I understood the ADL concept things shoul work in the
followin way.

I have a global ostream operator defined as

//ostreamtest.cpp
#include<iostream>
using namespace std;

ostream& operator<<(ostream& out,const string& str)
{
out<<"in ostream"<<endl;
out<<str.c_str()<<endl;

return out;
}

int main()
{

}

 

[Old Wolf]

As far as I understood the ADL concept things shoul work in the
followin way.

ostream& operator<<(ostream& out,const string& str)
{
out<<"in ostream"<<endl;
out<<str.c_str()<<endl;

return out;
}

This function will never be found for an expression like:
foo << bar;

because of ADL ! The arguments are all in namespace std,
so the compiler only searches namespace std. It doesn't
find your function that's in the global namespace.

Note that there is nothing you can do about this; trying
to add your function to namespace std would cause
undefined behaviour.