/*  sdfhypbc.cpp  by K.Tsuru  */
// function ID 3300 DRADIX
/*****************************************************************************
SDouble class
It provides the hyperbolic functions.
 cosh(x) and sinh(x) is set "ch" and "sh", respectively.
******************************************************************************/
#ifndef SN_H
#include "sn.h"
#endif
static SDouble sx = 0.0, scosh = 1.0, ssinh = 0.0;

SDouble CoshBS(const SDouble& x) {
    SDouble c, s;
    Hyperbolic(x, c, s);
    return c;
}
SDouble SinhBS(const SDouble& x) {
    SDouble c, s;
    Hyperbolic(x, c, s);
    return s;
}   
SDouble TanhBS(const SDouble& x) {
    SDouble c, s;
    Hyperbolic(x, c, s);
    return s*DReciprocal(c); // s/c
}   
void Hyperbolic(const SDouble& x, SDouble& ch, SDouble& sh) {
    if(!x.Sign(3300)){ // x = 0
        ch = scosh = 1.0;   sx = sh = ssinh = 0.0;
        return;
    }
    if( sx == x ) { // same value
        ch = scosh;  sh = ssinh;  return;
    }
    const double xMax = (double)DFIGURES*M_LN10*(double)DRADIX_EXP_MAX;  // = 301759.17...
//check the argument, e^x < DRADIX^DRADIX_EXP_MAX
    double xD = fabs( doubleD(x, 0) );
    if(xD > xMax) x.SetError(x.OVERFLOW_ERR, "Hyperbolic", 3300);

    SDouble r, dr;

    r = ExpBS(Dabs(x));     //r = e^|x|
    long ef=(long)x.MaxSize() - (long)r.NetRdxExp();
    if(ef <= 0) dr.SetZero();   //(1/r) is much less than r.
    else {
        RealSize C;
        C.SetEffFig(uint(ef));  //It can decrease the effective figures.
        dr = DReciprocal(r);    //dr = 1/(e^|x|)
        C.SetEffFig(0);
    }
    ch = r + dr;
    sh = r - dr;
    if(x.Sign() <0) sh.ChangeSign();
    scosh = ch = DsDiv(ch, 2);
    ssinh = sh = DsDiv(sh, 2);
}