igray.c

来自「c数值算法的源码」· C语言 代码 · 共 18 行

unsigned long igray(n,is)
int is;
unsigned long n;
{
	int ish;
	unsigned long ans,idiv;

	if (is >= 0)
		return n ^ (n >> 1);
	ish=1;
	ans=n;
	for (;;) {
		ans ^= (idiv=ans >> ish);
		if (idiv <= 1 || ish == 16) return ans;
		ish <<= 1;
	}
}