invert(x,p,n) that returns x with the n bits that begin at
position p inverted (i.e., 1 changed into 0 and vice versa), leaving the others unchanged.
unsigned invert(unsigned x, int p, int n)
{
return x ^ (~(~0U << n) << p);
}
/* main driver added, in a hurry while tired, by RJH. Better test driver suggestions are welcomed! */
#include <stdio.h>
int main(void)
{
unsigned x;
int p, n;
for(x = 0; x < 700; x += 49)
for(n = 1; n < 8; n++)
for(p = 1; p < 8; p++)
printf("%u, %d, %d: %u\n", x, n, p, invert(x, n, p));
return 0;
}