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what does !!a means in C programming

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
Dec 22 '09 #1
2 10447
donbock
2,426 Expert 2GB
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.
Dec 22 '09 #2
APmore
14
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.
Dec 26 '09 #3

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