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From:	Hans-Bernhard Broeker <broeker AT physik DOT rwth-aachen DOT de>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Fibonacci number
Date:	24 Feb 2004 16:38:31 GMT
Organization:	Aachen University of Technology (RWTH)
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To:	djgpp AT delorie DOT com
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Reply-To:	djgpp AT delorie DOT com

DJ Delorie <dj AT delorie DOT com> wrote:

> > Since negation is a well-defined operation on unsigned longs, there's
> > no error involved.

> This makes no sense.  

I would say it makes exactly as much sense as the fact that 

	unsigned long myvar = -1;

is perfectly legal C.  Some lints and picky compilers may warn about
it, but it's correct C.  

> *All* arithmetic operations are well defined for
> all integer types, but still, POSIX requires a range error.  

Are you sure it require an ERANGE for merely negative numbers, and not
just for values outside the range of +/- ULONG_MAX?  

At least P.J. Plauger's book on the ISO Standard libc implies
otherwise.  To quote him: "The function strtoul reports a range error
only if the converted magnitude is greater than ULONG_MAX, defined in
<limit.h>. ( Negating the value cannot cause overflow.)"

I think we can trust Plauger on this one --- he was in the X3J11
committee, after all.

-- 
Hans-Bernhard Broeker (broeker AT physik DOT rwth-aachen DOT de)
Even if all the snow were burnt, ashes would remain.

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