what does !!a means in C programming

[Dilip7597]

Hello Guys,

while checking one of the program, I found one difficulty with my program. there was a condition like (!!a), and I don't know what does it means. So if anybody knows about it then please help me out.

Thanks,
Dilip

[donbock]

The exclamation mark (!) is the logical "not" operator; for example, "!=". You have two of them strung together: !!a can be read as "not not a".

The truth table for the ! operator is something like this:
!(0) -> 1
!(any nonzero value) -> 0

Therefore, the double-not operator does this:
!!(0) -> 0
!!(any nonzero value) -> 1
That is, it changes any nonzero value to "1".

In my opinion, somebody was being overly clever.

[APmore]

That sort of coding is OK.it depends on the context of coding.

say he might be converting that decimal number to fit in binary logic.