/*  sdoplus.cpp  by K.Tsuru  */
// function ID = 330    DRADIX
/*********************************
SDouble class
It provides the addition operator+().
It returns m+n.
**********************************/
#ifndef SN_H
#include "sn.h"
#endif
SDouble operator+(const SDouble& m, const SDouble& n){
    if((m.Type() != m.REAL)||(n.Type() != n.REAL)) m.SetError(m.RADIX_ERR, "SD +", 330);
    int sgn = m.Sign(330) * n.Sign(330);
    if(sgn == 0){  //m=0 or n=0
        if( m.Sign() == 0 ) return n;
        else                return m;
    } else if (sgn > 0){    //same sign
        return DDAdd(m, n);
    } else {                //different sign
        int c = DDCompare(m, n);
       // m + n = m -(-n) = n-(-m)
        if(c > 0)   return DDSub(m, -n);    //|m|>|n|, The sign is the same as that of m, set in DDSub()
        else if(c)  return DDSub(n, -m);    //|m|<|n|, sign same as n
        else return 0.0;    // c = 0 : m = n  result = 0
    }
}