Noalias trivia question

[hutchson at convex.UUCP]

For a less contrived example:

   for (i=n; i; i--) a[i]=i;   /* each number in (i:n) occurs once in a. */
   shuffle(a);                 /* randomly or not--doesn't matter. */
   ...
Now, the programmer knows full well that i!=j implies a[i]!=a[j].
But try explaining that to your favorite optimizer.  Better hope it
understands second-order logic.  If you really want a challenge, try letting
it figure it out for itself.  Remember that this property of a is not
created, but is maintained, by "shuffle".

Such code would be found somewhere in, say, a blackjack simulation.  I suspect
that properties of permutations of arrays might be useful in more productive
programs also.