#include "libm.h" double trunc(double x) { union {double f; uint64_t i;} u = {x}; int e = (int)(u.i >> 52 & 0x7ff) - 0x3ff + 12; uint64_t m; if (e >= 52 + 12) return x; if (e < 12) e = 1; m = -1ULL >> e; if ((u.i & m) == 0) return x; FORCE_EVAL(x + 0x1p120f); u.i &= ~m; return u.f; }