Is !! a safe way to convert to bool in C++?

Question

[This question is related to but not the same as this one.]

If I try to use values of certain types as boolean expressions, I get a warning. Rather than su

Answer 1

Disable the warning.

Write for clarity first; then profile; then optimize for speed, where required.

Answer 2

All valid techniques, all will generate the same code.

Personally, I just disable the warning so I can use the cleanest syntax. Casting to a bool is not something I'm worried about doing accidentally.

Answer 3

!! may be compact, but I think it is unnecessarily complicated. Better to disable the warning or use the ternary operator, in my opinion.

Answer 4

Yes it is safe.

0 is interpreted as false, everthing else is true,
hence !5 comes out as a false
!0 comes out as true
so !!5 comes out as true

Answer 5

I really hate !!t!!!!!!. It smacks of the worst thing about C and C++, the temptation to be too clever by half with your syntax.

bool b(t != 0); // Is the best way IMHO, it explicitly shows what is happening.