Basic Math (STL Sample)

The sample code below illustrates how to use some basic math functions in Visual C++.

Required Header:
< functional >

template<class _TYPE>
     struct plus : binary_function<_TYPE, _TYPE, _TYPE>
     {
        _TYPE operator()(const _TYPE& _X, const _TYPE& _Y) const
                                         {return (_X + _Y); }
     };
template<class _TYPE>
     struct minus : binary_function<_TYPE, _TYPE, _TYPE>
     {
        _TYPE operator()(const _TYPE& _X, const _TYPE& _Y) const
                                         {return (_X - _Y); }
     };
template<class _TYPE>
     struct times : binary_function<_TYPE, _TYPE, _TYPE>
     {
       _TYPE operator()(const _TYPE& _X, const _TYPE& _Y) const
                                         {return (_X * _Y); }
     };
template<class _TYPE>
     struct divides : binary_function<_TYPE, _TYPE, _TYPE>
     {
       _TYPE operator()(const _TYPE& _X, const _TYPE& _Y) const
                                         {return (_X / _Y); }
     };
template<class _TYPE>
     struct modulus : binary_function<_TYPE, _TYPE, _TYPE>
     {
       _TYPE operator()(const _TYPE& _X, const _TYPE& _Y) const
                                         {return (_X % _Y); }
     };

Note: The class/parameter names in the prototype do not match the version in the header file. Some have been modified to improve readability.

Description:
This sample uses a class derived from all five basic math structures: plus, minus, times, divides, and modulus, using an integer as the templated operand.

Sample Code:

////////////////////////////////////////////////////////////////
//
// Compile options needed: none
//
// mathfunc.cpp - Illustrating the basic STL math
//                functions.
//
// Structures: plus<A>    - Adds data type A object to
//                          a class object derived from plus.
//             minus<A>   - Subtracts data type A.
//             multiplies<A>   - Multiplies object by data type A.
//             divides<A> - Divides object by data type A.
//             modulus<A> - Returns object modulo A.
/////////////////////////////////////////////////////////////////

#include <functional>
#include <iostream>

using namespace std ;

class MathOps : public plus<int>, public minus<int>,
                 public multiplies<int>, public divides<int>,
                 public modulus<int>
{
public:
  int value;
  MathOps(){value=0;}
  MathOps(int x){value=x;}
  result_type operator+(second_argument_type add2)
                            {return value + add2;}
  result_type operator-(second_argument_type sub2)
                            {return value - sub2;}
  result_type operator*(second_argument_type mult2)
                            {return value * mult2;}
  result_type operator/(second_argument_type div2)
                            {return value / div2;}
  result_type operator%(second_argument_type mod2)
                            {return value % mod2;}
  friend ostream& operator<<(ostream& os, const MathOps& obj ) ;
};

ostream& operator<<(ostream& os, const MathOps& obj )
{
       os << obj.value ;
       return os ;
}

void main(void)
{
  MathOps one,two,three,four,five,six;

  cout << "Using MathOps class..." << endl ;

  one = 18;
  cout << "one = " << one << endl ;

  two = one + 1;
  cout << "two = one + 1 = " << two << endl ;

  three = two - 2;
  cout << "three = two - 2 = " << three << endl ;

  four = three * 3;
  cout << "four = three * 3 = " << four << endl ;

  five = four / 4;
  cout << "five = four / 4 = " << five << endl ;

  six = five % 5;
  cout << "six = five % 5 = " << six << endl ;
}

 

Program Output is:

Using MathOps class...
one = 18
two = one + 1 = 19
three = two - 2 = 17
four = three * 3 = 51
five = four / 4 = 12
six = five % 5 = 2