不用+-*/%实现整数的+-*/%运算

可能计算机相关专业有教授过相关的知识，这里只是作为一个非计算机专业人员的实现方法，模仿十进制的相关运算方法加以实现：

#include <iostream>using std::cout;using std::endl;using std::ostream;struct divide_modulo_zero_exception{    static const char msg[64];};const char divide_modulo_zero_exception::msg[] =    "exception: attempt to divide/modulo integer by 0.";class Integer{public:    explicit Integer(int value = 0);    Integer(const Integer &);    Integer & operator = (const Integer &);    ~Integer();public:    const Integer & operator + () const;    Integer operator - () const;    Integer operator + (const Integer &) const;    Integer operator - (const Integer &) const;    Integer operator * (const Integer &) const;    Integer operator / (const Integer &) const;    Integer operator % (const Integer &) const;    ostream & operator << (ostream & os) const;private:    int add(int, int) const;    int sub(int, int) const;    int mul(int, int) const;    int div(int, int) const;    int mod(int, int) const;    void div_mod(int, int, int &, int &) const;private:    int m_value;};Integer::Integer(int value) : m_value(value){}Integer::Integer(const Integer & other) : m_value(other.m_value){}Integer & Integer::operator = (const Integer & other){    if (&other != this)    {        m_value = other.m_value;    }    return(*this);}Integer::~Integer(){}const Integer & Integer::operator + () const{    return(*this);}Integer Integer::operator - () const{    return(Integer(add(~m_value, 1)));}Integer Integer::operator + (const Integer & other) const{    return(Integer(add(m_value, other.m_value)));}Integer Integer::operator - (const Integer & other) const{    return(Integer(sub(m_value, other.m_value)));}Integer Integer::operator * (const Integer & other) const{    return(Integer(mul(m_value, other.m_value)));}Integer Integer::operator / (const Integer & other) const{    return(Integer(div(m_value, other.m_value)));}Integer Integer::operator % (const Integer & other) const{    return(Integer(mod(m_value, other.m_value)));}int Integer::add(int a, int b) const{    /*    return(a + b);    */    while (0 != a && 0 != b)    {        int x = (a ^ b);        int y = (a & b) << 1;        a = x;        b = y;    }    return(0 != a ? a : b);}int Integer::sub(int a, int b) const{    /*    return(a - b);    */    return(add(a, add(~b, 1)));}int Integer::mul(int a, int b) const{    /*    return(a * b);    */    bool s = false;    if (a < 0)    {        a = add(~a, 1);        s = !s;    }    if (b < 0)    {        b = add(~b, 1);        s = !s;    }    int x = 0;    int y = a;    while (0 != b)    {        if (0 != (b & 1))        {            x = add(x, y);        }        b >>= 1;        y <<= 1;    }    if (s)    {        x = add(~x, 1);    }    return(x);}void Integer::div_mod(int a, int b, int & d, int & m) const{    if (0 == b)    {        throw divide_modulo_zero_exception();    }    int s = 0;    if (a < 0)    {        a = add(~a, 1);        s |= 1;    }    if (b < 0)    {        b = add(~b, 1);        s |= 2;    }    d = 0;    m = 0;    int x = (1 << sub(sizeof(int) << 3, 2));    while (0 != x)    {        m <<= 1;        if (a & x)        {            m |= 1;        }        d <<= 1;        if (m >= b)        {            d |= 1;            m = sub(m, b);        }        x >>= 1;    }    if (1 == s || 2 == s)    {        d = add(~d, 1);    }    if (0 != (s & 1))    {        m = add(~m, 1);    }}int Integer::div(int a, int b) const{    /*    return(a / b);    */    int d = 0;    int m = 0;    div_mod(a, b, d, m);    return(d);}int Integer::mod(int a, int b) const{    /*    return(a % b);    */    int d = 0;    int m = 0;    div_mod(a, b, d, m);    return(m);}ostream & Integer::operator << (ostream & os) const{    return(os << m_value);}ostream & operator << (ostream & os, const Integer & number){    return(number << os);}void test(const Integer & a, const Integer & b){    Integer c;    cout << "--------------------" << endl;    c = a + b;    cout << a << " + " << b << " = " << c << endl;    c = a - b;    cout << a << " - " << b << " = " << c << endl;    c = a * b;    cout << a << " * " << b << " = " << c << endl;    c = a / b;    cout << a << " / " << b << " = " << c << endl;    c = a % b;    cout << a << " % " << b << " = " << c << endl;    cout << "--------------------" << endl;}int main(int argc, char * argv[]){    Integer i(55);    Integer j;    Integer k;    cout << "--------------------" << endl;    cout << "i = " << i << endl;    j = +i;    cout << "j = +i = " << j << endl;    k = -i;    cout << "k = -i = " << k << endl;    cout << "--------------------" << endl;    Integer result;    Integer x(19);    Integer y(28);    test(x, y);    test(y, x);    int a[] = { 5, 5, -5, -5 };    int b[] = { 3, -3, 3, -3 };    for (int i = 0; i < 4; ++i)    {        x = Integer(a[i]);        y = Integer(b[i]);        test(x, y);        test(y, x);    }    try    {        Integer(4) % Integer(0);    }    catch (const divide_modulo_zero_exception & e)    {        cout << e.msg << endl;        return(1);    }    return(0);}