| #include "libm.h" |
| |
| double nextafter(double x, double y) { |
| union { |
| double f; |
| uint64_t i; |
| } ux = {x}, uy = {y}; |
| uint64_t ax, ay; |
| int e; |
| |
| if (isnan(x) || isnan(y)) |
| return x + y; |
| if (ux.i == uy.i) |
| return y; |
| ax = ux.i & -1ULL / 2; |
| ay = uy.i & -1ULL / 2; |
| if (ax == 0) { |
| if (ay == 0) |
| return y; |
| ux.i = (uy.i & 1ULL << 63) | 1; |
| } else if (ax > ay || ((ux.i ^ uy.i) & 1ULL << 63)) |
| ux.i--; |
| else |
| ux.i++; |
| e = ux.i >> 52 & 0x7ff; |
| /* raise overflow if ux.f is infinite and x is finite */ |
| if (e == 0x7ff) |
| FORCE_EVAL(x + x); |
| /* raise underflow if ux.f is subnormal or zero */ |
| if (e == 0) |
| FORCE_EVAL(x * x + ux.f * ux.f); |
| return ux.f; |
| } |
