Argument Matching and the this Pointer
Class member functions are treated differently, depending on whether they are declared as static. Because nonstatic functions have an implicit argument that supplies the this pointer, nonstatic functions are considered to have one more argument than static functions; otherwise, they are declared identically.
These nonstatic member functions require that the implied this pointer match the object type through which the function is being called, or, for overloaded operators, they require that the first argument match the object on which the operator is being applied. (For more information about overloaded operators, see Overloaded Operators.)
Unlike other arguments in overloaded functions, no temporary objects are introduced and no conversions are attempted when trying to match the this pointer argument.
When the – > member-selection operator is used to access a member function, the this pointer argument has a type of class-name * const. If the members are declared as const or volatile, the types are const class-name ** * const and volatile class-name * const, respectively.
The . member-selection operator works exactly the same way, except that an implicit & (address-of) operator is prefixed to the object name. The following example shows how this works:
// Expression encountered in code
obj.name
// How the compiler treats it
(&obj)->name
The left operand of the –>* and .* (pointer to member) operators are treated the same way as the . and –> (member-selection) operators with respect to argument matching.