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

#include "libm.h"

#if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
long double tanhl(long double x)
{
        return tanh(x);
}
#elif LDBL_MANT_DIG == 64 && LDBL_MAX_EXP == 16384
long double tanhl(long double x)
{
        union ldshape u = {x};
        unsigned ex = u.i.se & 0x7fff;
        unsigned sign = u.i.se & 0x8000;
        uint32_t w;
        long double t;

        /* x = |x| */
        u.i.se = ex;
        x = u.f;
        w = u.i.m >> 32;

        if (ex > 0x3ffe || (ex == 0x3ffe && w > 0x8c9f53d5)) {
                /* |x| > log(3)/2 ~= 0.5493 or nan */
                if (ex >= 0x3fff+5) {
                        /* |x| >= 32 */
                        t = 1 + 0/(x + 0x1p-120f);
                } else {
                        t = expm1l(2*x);
                        t = 1 - 2/(t+2);
                }
        } else if (ex > 0x3ffd || (ex == 0x3ffd && w > 0x82c577d4)) {
                /* |x| > log(5/3)/2 ~= 0.2554 */
                t = expm1l(2*x);
                t = t/(t+2);
        } else {
                /* |x| is small */
                t = expm1l(-2*x);
                t = -t/(t+2);
        }
        return sign ? -t : t;
}
#elif LDBL_MANT_DIG == 113 && LDBL_MAX_EXP == 16384
// TODO: broken implementation to make things compile
long double tanhl(long double x)
{
        return tanh(x);
}
#endif