source: asp3_tinet_ecnl_rx/trunk/musl-1.1.18/src/math/nexttoward.c@ 337

#include "libm.h"

#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