Question

Possible Duplicate:
Double Negation in C++ code

As far as I know, no C/C++ books tutorials or manuals mention this technique. Maybe because it’s just a tiny little thing, not worth mentioning.

I use it because C/C++ mixes bool type with int, long, pointer, double etc…together. It’s very common to need to convert a non-bool to bool. It’s not safe to use (bool)value to do that, so I use !! to do it.

Example:

bool bValue = !!otherValue;

Answer 1

I think !! is quite clear in comparison to some of the other choices such as :

if (foo)
  bar = 1;
else
  bar = 0;

or bar = foo ? 1 : 0;

Since !! does exactly one thing, I find it very unambiguous.