/*  sdfcosSR.cpp  by K.Tsuru  */
// function ID 3104     DRADIX
/*****************************
SDouble class
trigonometric function cos x
using sereies and reduction method
enum { COS_CALC = 1, SIN_CALC = 2, TAN_CALC = 3, COT_CALC = 4};
******************************/
#ifndef SN_H
#include "sn.h"
#endif
#define usesCosSeriesInCos 1
SDouble CosS_RN(const SDouble& x){
    if(x.Sign(3104) == 0) return 1.0;       // x = 0
#if usesCosSeriesInCos
    // |x| is very small.
    if(x.NetRdxExp() < -4) return CosSeries(x); // |x| < 1.0e-16  ver.2.18

    uint fig = x.Last() - x.First() +1u;
    double c;

    if(fig <= 5u){  // x is a short number.
        double dblX = doubleD(x, 0), absX = fabs(dblX);
        // y is short and small, then call CosSeries()
        c = (absX > M_PI_4) ? 1.0 : log10((double)x.MaxSize()*absX) - 2.5;
        if(c < 0) return CosSeries(x);
    }
#endif
    SDouble y, r;
    int func = COS_CALC;
    int sgn = GetTriCalcMethod(x, y, &func);    // |y| < pi/4

    if(sgn == 0){   // y = -1, 0, 1
        x.upToTerm = 0;
        return y;
    }
#if usesCosSeriesInCos
    // y is long but small.
    double dblY = doubleD(y, 0), absY = fabs(dblY);
    c = (double)x.MaxSize()/64 + log10(absY) + 0.5;
    if(c < 0){
        if(func == COS_CALC) r = CosSeries(y);
        else r = SinSeries(y);
        goto Ret;
    }
#endif
//RN : using x/R^n reduction method
    if(func == COS_CALC) r = CosRN(y);
    else  r = SinRN(y);
Ret:
    if(sgn < 0) r.ChangeSign();     // r = -r;
    return r;
}