Использование остатка от деления Оо

#ifndef _STONEWT_H_
#define _STONEWT_H_
class Stonewt
{
private:
    enum    {Lbs_per_stn=14};
    int stone;
    double pds_left;
    double pounds;
    char mode;
public:
    Stonewt(double lbs,char form='p');
    Stonewt(int stn,double lbs,char form='p');
    Stonewt();
    ~Stonewt();
    void pounds_mode();
    void stone_mode();
    operator int() const;
    operator double() const;
    Stonewt operator+(const Stonewt &st) const;
    Stonewt operator-(const Stonewt &st) const;
    Stonewt operator*(double n) const;
    friend ostream & operator<<(ostream& os,const Stonewt & st);
};
#endif

#include <iostream>
using namespace std;
#include "Stonewt.h"
Stonewt::Stonewt(double lbs,char form)
{
    stone=int(lbs)/Lbs_per_stn;
    pds_left=int(lbs)%Lbs_per_stn+lbs-int(lbs);
    pounds=lbs;
}
Stonewt::Stonewt(int stn, double lbs,char form)
{
    stone=stn;
    pds_left=lbs;
    pounds=stn*Lbs_per_stn+lbs;
}
Stonewt::Stonewt()
{
    stone=0;
    pounds=0;
    pds_left=0;
}
Stonewt::~Stonewt()
{
}
void Stonewt::pounds_mode()
{
    mode='p';
}
void Stonewt::stone_mode()
{
    mode='s';
}
Stonewt::operator int() const
{
    return int(pounds+0.5);
}
Stonewt::operator double() const
{
    return pounds;
}
Stonewt Stonewt::operator+(const Stonewt &st) const
{
    Stonewt sum;
    sum.pounds=pounds+sum.pounds;
    sum.stone=stone+st.stone+sum.pounds/Lbs_per_stn;
    sum.pounds%=Lbs_per_stn;
}
Stonewt Stonewt::operator -(const Stonewt &st) const
{
    Stonewt diff;
    int tot1,tot2;
    tot1=pounds+stone*Lbs_per_stn;
    tot2=st.pounds+st.stone*Lbs_per_stn;
    diff.pounds=(tot1-tot2)%Lbs_per_stn;
    diff.stone=(tot1-tot2)/Lbs_per_stn;
    return diff;
}
Stonewt Stonewt::operator *(double n) const
{
    Stonewt multip;
    double totalpounds=stone*Lbs_per_stn*n+pounds*n;
    multip.stone=totalpounds/Lbs_per_stn;
    multip.pounds=totalpounds%Lbs_per_stn;
    return multip;
}
ostream & operator <<(ostream & os,const Stonewt &t)
{
    if(t.mode=='s')
        os<<t.stone<<" stones, "<<t.pounds<<" pounds.\n";
    else if(t.mode=='p')
        os<<t.pounds<<" pounds.\n";
    return os;
}

#include <iostream>
using namespace std;
#include "Stonewt.h"
int main()
{
    Stonewt jackie=Stonewt(250.6);
    Stonewt dave=Stonewt(13,5,'s');
    cout<<jackie;
    jackie.stone_mode();
    cout<<jackie;
    jackie.pounds_mode();
    Stonewt catie;
    cout<<catie;
    catie=jackie-dave;
    cout<<catie;
    catie=jackie+dave;
    cout<<catie;
    system("pause");
    return 0;
}