Calling primitive operator-functions explicitly in C++

Question

int a, b, c; 

//do stuff. For e.g., cin >> b >> c; 

c = a + b;          //works 
c = operator+(a,b); //fails to compile, \'operator+\' not defined. 
         


        

Answer 1

Firstly, invoking built-in operators as functions will not work simply because the language specification never says that such functions exist. Built-in operators are just operators. There are no implementing functions behind them simply because the language specification never suggests their existence. Function-based implementations are specific to overloaded operators only.

Secondly, during overload resolution the built-in operators are indeed represented by their imaginary function-like counterparts, but the wording that prohibits "explicit" function-like invocation of built-in operators is present in 13.6/1

The candidate operator functions that represent the built-in operators defined in clause 5 are specified in this subclause. These candidate functions participate in the operator overload resolution process as described in 13.3.1.2 and are used for no other purpose.