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Last active Mar 8, 2017
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cross-platform first set bit
#include <stdio.h>
#include <stdlib.h>
typedef unsigned int MVMuint32;
#ifdef __GNUC__
#define FFS(x) __builtin_ffs(x)
#elif defined(_MSC_VER)
static inline MVMuint32 FFS(MVMuint32 x) {
MVMuint32 i = 0;
if (_BitScanForward(&i, x) == 0)
return 0;
return i + 1;
#error "Can't define Find First Set"
int main (int argc, char **argv) {
int v, f;
if (argc < 2)
return 0;
v = atoi(argv[1]);
f = FFS(v);
fprintf(stderr, "%d %d\n", v, f);
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