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| From | John Gordon <gordon@panix.com> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: behavior of || operator |
| Date | 2011-10-07 18:47 +0000 |
| Organization | PANIX Public Access Internet and UNIX, NYC |
| Message-ID | <j6nhgo$bm3$1@reader1.panix.com> (permalink) |
| References | <j6nc0d$dii$1@speranza.aioe.org> |
In <j6nc0d$dii$1@speranza.aioe.org> "Mark" <mark_cruzNOTFORSPAM@hotmail.com> writes:
> #define ATTACH 1
> #define DETACH 2
> if ((action != ATTACH) || (action != DETACH))
> puts("invalid action");
> I appears that condition within if() is verified for being TRUE or FALSE,
> and it is sufficient to have just one operand of || operator to return TRUE
> in order for the whole expression yield TRUE result.
> To make it right, || must be replaced with &&.
> Is my reasoing above correct and valid?
You should use && instead of ||, yes.
But not because of the behavior you describe above; using || is simply
incorrect logic.
No matter what value action has, it will ALWAYS be either unequal to 1 or
unequal to 2. Using || is just wrong. You want to know when it is unequal
to 1 AND unequal to 2.
--
John Gordon A is for Amy, who fell down the stairs
gordon@panix.com B is for Basil, assaulted by bears
-- Edward Gorey, "The Gashlycrumb Tinies"
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behavior of || operator "Mark" <mark_cruzNOTFORSPAM@hotmail.com> - 2011-10-07 13:13 -0400 Re: behavior of || operator James Kuyper <jameskuyper@verizon.net> - 2011-10-07 14:11 -0400 Re: behavior of || operator John Gordon <gordon@panix.com> - 2011-10-07 18:47 +0000 Re: behavior of || operator Willem <willem@toad.stack.nl> - 2011-10-07 19:50 +0000 Re: behavior of || operator Gene <gene.ressler@gmail.com> - 2011-10-08 13:58 -0700
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