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Subject: Re: comparing signed and unsigned integral values
Date: Tue, 31 Dec 2002 05:42:10 +0000 (UTC)
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Allan W wrote:
> I've heard C++'s rules described as "preserved unsignedness." In other
> words, if one of your variables is unsigned, your comparisons will be
> unsigned.

That's not quite true.  C++ (and also ANSI C, from which the C++ rules
were inherited) requires that conversions be value-preserving whenever
possible.  For example, in a mixed expression containing int and
unsigned short everything will be promoted to int if possible, i.e.,
if sizeof(int) > sizeof(short);  but it sizeof(short) = sizeof(int)
everything gets promoted to unsigned int.  K&R C's rules, which were
unsigned-preserving, would have everything promoted to unsigned int
no matter what.

I know why the language is the way it is, but I often find myself
wishing that the rules were different and that all the integral
types had to be subranges of a signed type of maximum size so
that all conversions would be value-preserving.

nobody

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