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 versions of && and || first evaluate their left-hand expression, and if that fully determines the result (false for &&, true for ||) then the right-hand expression doesn’t need to be evaluated—and is guaranteed not to be. We all get so used to this handy feature that we routinely allow the correctness of the right-hand side depend on the success of the left-hand side: