Re: !!, what is it?

Cafer Şimşek wrote: 
"Mike Wahler" <mkwahler@xxxxxxxxxxxx> writes:


[...]


No, ! is an operator. It's result is always either zero or one. 

                                                      ^^^^^^^^^^^^

I think, C standarts says something about logical operations resusts;
if the result is false, it's value is 0 (zero). if the result is true,
it's value is non-zero (like -2, -1, 2, 3, ...). So, it must NOT be
one. This difference has seen according to compiler or target
platform.

Incorrect. The result of any logical operator is *always* 0 or 1 and this is defined by the standard. What probably has you confused is that any non-zero value will act as true, so all the values you quote will act as true. However, I repeat, the boolean operators will never return any value other than 0 or 1 on *any* implementation.

For example; some compiler's headers provide TRUE and FALSE constants
like that;

#define FALSE 0
#define TRUE !FALSE

// or

#define TRUE (0==0)
#define FALSE !TRUE


In both cases you are guaranteed that TRUE == 1.
--
Flash Gordon
Living in interesting times.
Although my email address says spam, it is real and I read it.
.

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