Question

Normally you can compare strings..

if (var1 == "a string") ...

But when I declare my own class with the conversion operator, like this :

class my_type {
   operator std::string() const { ... };
   ....
}

Now this :

 std::string var1("a string");
 my_type x("a string");
 if (x == "a string") ....
 if (x == var1) ....

does not work.. i.e….

error: no match for ‘operator==’ 

Of course this works :

 if ((std::string) x == var1) ....

But I want it to happen w/o explicitly casting.
why does not c++ convert my_type to string for comparison..
How can I force it to do this w/o implementing the “==” operator itself ?
The same goes for the other comparison operators.

thank you

PS> Btw if I implement operator which convert my_type to numbers(it is OK for my type)…like :

 operator double() const { ... };

the comparison with numbers work ok, I don’t need to implement ==,etc…..

Answer 1

As pointed out here, this isn’t about implicit casts, but of how operator == behaves on strings.

I however suggest you overload operator == for your class and not rely on an implicit conversion.