> 2. A null pointer constant or value of type nullptr_t may be converted to nullptr_t
and elsewhere
> 6.5.4.3 Unary arithmetic operators
> [...]
> 5. The result of the logical negation operator ! is 0 if the value of its operand compares unequal to 0, 1 if the value of its operand compares equal to 0. The result has type int. The expression !E is equivalent to (0==E)
3/