/*  sxfbexpx.cpp  by K.Tsuru  */
// function ID 5205  BRADIX(reference)
/*****************
SDecimal class
exp(x) by series
******************/
#ifndef SN_H
#include "sn.h"
#endif
static const char* func = "BexpSeries";
SDecimal BexpSeries(const SDouble& x){
    int e = x.NetRdxExp();
    int xsgn;
    if( (xsgn = x.Sign(5205)) == 0) return x;
    if( e > 0){ // x > 1
        x.SetError(x.OUT_OF_RANGE, func, 5205);
    }

    SDecimal sum(1.0), xf, delta;
    xf = xf.ConvToBin(x);
    ulong mt = delta.SlOpMaxValue(), k = 2;

//  sum = 1 + x;
    if(xsgn < 0 ){
        xf.ChangeSign();    XXSub(sum, xf, sum);    // xf = |x|
    } else XXAdd(sum, xf, sum);
    delta = xf;

    while(delta.Sign()){
        XsDiv(delta*xf, k, delta);
        if((xsgn < 0) && (k & 1)) XXSub(sum, delta, sum);
        else XXAdd(sum, delta, sum);
        if( (k++) >= mt ){
            sum.SetError(sum.NOT_CONVERGE, func, -5205);
            break;
        }
    }
    return sum;
}