Subj : Re: Reversing a number
To   : comp.programming
From : Peter Nilsson
Date : Tue Sep 13 2005 01:12 am

zeroxia@gmail.com wrote:
> Is this implementation not compiler-specific?
> (For example, the case of which i is negative.
>
> int reverse(int i)
> {
<snip>
      int n = 0;
>     while (i)
>     {
>         n *= 10;
>         n += i % 10;
>         i /= 10;

This can cause problems in the 1990 flavour of C as the
rounding of division is implementation defined if either
operatand is negative.

In other words, -4 % 10 may produce +6 rather than -4. On such
a machine, you get an indefinite loop, and consequent overflow,
since -1/10 is just -1 again.

>     }
>     return n;
> }

-- 
Peter

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