multiplies


class template
<functional>
template <class T> struct multiplies;

Multiplication function object class

This class defines function objects for the multiplication arithmetic operation.

Generically, function objects are instances of a class with member function operator() defined. This member function allows the object to be used with the same syntax as a regular function call, and therefore it can be used in templates instead of a pointer to a function.

multiplies has its operator() member defined such that it returns the product of its two arguments.

This class is derived from binary_function and is defined as:

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template <class T> struct multiplies : binary_function <T,T,T> {
  T operator() (const T& x, const T& y) const
    {return x*y;}
};


Objects of this class can be used with some standard algorithms such as transform or accumulate.

Members

T operator() (const T& x, const T& y)
Member function returning the product of its two arguments (x*y).


Example

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// factorials (multiplies example)
#include <iostream>
#include <functional>
#include <numeric>
using namespace std;

int main () {
  int numbers[9];
  int factorials[9];
  for (int i=0;i<9;i++) numbers[i]=i+1;
  partial_sum ( numbers, numbers+9, factorials, multiplies<int>() );
  for (int i=0; i<9; i++)
    cout << numbers[i] << "! is " << factorials[i] << "\n";
  return 0;
}


Output:

1! is 1
2! is 2
3! is 6
4! is 24
5! is 120
6! is 720
7! is 5040
8! is 40320
9! is 362880


See also

plus Addition function object class (class template)
minus Subtraction function object class (class template)
divides Division function object class (class template)
modulus Modulus function object class (class template)
negate Negative function object class (class template)
equal_to Function object class for equality comparison (class template)
binary_function Binary function object base class (class template)