C++ Coding Standards: 101 Rules, Guidelines, and Best Practices

30. Avoid overloading &&, ||, or , (comma)

Summary

Wisdom means knowing when to refrain: The built-in &&, ||, and , (comma) enjoy special treatment from the compiler. If you overload them, they become ordinary functions with very different semantics (you will violate Items 26 and 31), and this is a sure way to introduce subtle bugs and fragilities. Don’t overload these operators naïvely.

Discussion

The primary reason not to overload operator&&, operator||, or operator, (comma) is that you cannot implement the full semantics of the built-in operators in these three cases, and programmers commonly expect those semantics. In particular, the built-in versions evaluate left-to-right, and for && and || also use short-circuit evaluation.

The built-in ...