Re: lun - Lucky Number

Richard Heathfield in sci.crypt:

[...]

I knocked up a quick sieve for you so that you can see the macros
being used in another context - here, to tick off compounds (by
which I mean non-primes) a la Eratosthenes.

It works. :-)

                                           (I also fixed a tiny
and probably harmless bug in BIT_QRY, where x was insufficiently
parenthiprotected.)
>
#include <stdio.h>
>
#define BIT_QRY(x,i) (((x)[(i)>>3] & (1<<((i)&7)))!=0)

This is actually another C question:

Why does it have to be "(x)" and "(i)" everywhere instead of
"x" and "i"? What kind of "protection" is meant here?

Marcel
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