swap() macro

[Ben Cranston]

Paul Schauble <Schauble at mit-multics.arpa> asks:
> Can someone construct a version that makes
>     int *a, *b;
>     swap (*a++,*b++);
>> work right?

Steve Villee <ihnp4!mot!anasazi!steve> replies:

> #define swap(x, y) \
>   if (1) \
>   { \
>     register int *xp, *yp, t; \
>     xp = &(x); \
>     yp = &(y); \
>     t = *xp; \
>     *xp = *yp; \
>     *yp = t; \
>   } \
>   else

and goes on to site some special cases in which the "if" implementation 
is a big win.  Other examples have also been given.

Since the original question was about swapping (int *)s, why do not the
given examples involve (int **)s, i.e. pointers to pointers to ints?

Nailing jelly to a tree again...

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Ben Cranston zben @ umd2.UMD.EDU    Kingdom of Merryland Sperrows 1100/92
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