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#include "libm.h" // for FORCE_EVAL
#include <float.h> // for LDBL_MANT_DIG, LDBL_MAX_EXP
#include <math.h> // for signbit, isnan, nexttoward
#include <stdint.h> // for uint64_t
#if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
double nexttoward(double x, long double y)
{
return nextafter(x, y);
}
#else
double nexttoward(double x, long double y)
{
union {
double f;
uint64_t i;
} ux = { x };
int e;
if (isnan(x) || isnan(y))
return x + y;
if (x == y)
return y;
if (x == 0) {
ux.i = 1;
if (signbit(y))
ux.i |= 1ULL << 63;
} else if (x < y) {
if (signbit(x))
ux.i--;
else
ux.i++;
} else {
if (signbit(x))
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;
}
#endif
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