/* Copyright (C) 1994 DJ Delorie, see COPYING.DJ for details */
#include <math.h>

double tanh(double x)
{
    if (x > 50)
        return 1;
    else if (x < -50)
        return -1;
    else {
        const double ebig = exp(x);
        const double esmall = 1.0 / ebig;
        return (ebig - esmall) / (ebig + esmall);
    }
}