what is the difference between user-defined conversion and user-defined operator?

Question

In the context of operator overloading, what is the difference between user-defined conversion and user-defined operator?

Answer 1

A user-defined conversion is either:

• A constructor in the destination type which can be called with a single parameter of the source type (more arguments can exist if they have default values)

or

• A non-static member function of the source type with the name operator DESTTYPE()

As you can see, the second option uses the operator keyword just as is used when overloading the traditional operators.

(Note: All of this is formally described in section [class.conv] of the C++ standard.)

Answer 2

In C++, there is no concept of user-defined operators that can be overloadable. Only existing operators, with an exception of few( ., .*, ::, ?:, sizeof ), can be overloaded.