/*  slfllsub.cpp  by K.Tsuru  */
// function ID = 208  DRADIX, BRADIX
/*************************************************************
SLong and SInteger classes
m - n ( m and n have the same sign, and |m|>|n|>0).
*************************************************************/
#ifndef SN_H
#include "sn.h"
#endif

static const char* const func = "\'-\' or LLSub";
SLong LLSub(const SLong& m, const SLong& n) {
    if( m.Sign() != n.Sign() ) m.SetError(m.SYNTAX_ERR, func, 208);
    SLong result(m);    // result = m

    if( (n.aHead > 0) && ( m.Radix() != n.Radix() ) ){
        m.SetError(m.RADIX_ERR, func, 208);
    }

    int k = 0;
    long rdx = (long)m.Radix();
    long w;
    const fType* mv = m.ReadFigures();
    const fType* nv = n.ReadFigures();
    fType* rv = result.figure.Elements();                //*
// Here, result = m.
    uint i;
    for(i = n.aTail; i <= n.aHead ; i++){
        w = (long)mv[i] - (long)nv[i] + k;  // -radix <= w < radix
        if( w < 0 ) { k = -1;  w += rdx;
        } else        k = 0;
        rv[i] = (fType)w;
    }
    for( ; k && (i<= m.aHead); i++){
    //Here nv[i] = 0.
        w = (long)mv[i] + k;
        if( w < 0 ) { k = -1;  w += rdx;
        } else        k = 0;
        rv[i] = (fType)w;
    }
    if(k) m.SetError(m.SYNTAX_ERR, func, 208);
//It gets the figure position.
    uint rh = m.aHead, rt = min(m.Tail(), n.Tail());    // aTail --> Tail() since ver 2.191
#ifndef NDEBUG
result.figure(rh);
#endif
    while(!rv[rh]) rh--;
    while(!rv[rt]) rt++;
    result.aHead = rh;
    result.aTail = rt;
    result.SetSign(m.Sign());
    result.DoCutDown();     //It reduces the size if possible.

    return result;
}