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#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;
}
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