/*  sdfqrrt.cpp  by K.Tsuru  */
// function ID = 3012  DRADIX only
/****************************
SDouble class
quartic root of a
It returns a*{RecQrrt(a)}^3.
*****************************/
#ifndef SN_H
#include "sn.h"
#endif
static const char* const func = "Qrrt";

SDouble Qrrt(const SDouble& a){
    SDouble d, y;
    y = RecQrrt(a); // if a < 0 causes an error
    y = a*Dpow(y, 3);
    if(y.Verify()){     // check |a - y^3| << a ?
        d = y*y;    d = d*d;
        d = a - d;
        if(!d.IsMLT(a)){  //It sees the relative error. d << a ?
            y.SetError(y.VERIFY, func, 3012);
        }
    }
    return y;
}