C++

Reference

<functional>

class template
<functional>

std::multiplies

template <class T> struct multiplies;
Multiplication function object class
Binary function object class whose call returns the result of multiplying its two arguments (as returned by operator *).

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 function call.

It is defined with the same behavior 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;}
};
 
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template <class T> struct multiplies {
  T operator() (const T& x, const T& y) const {return x*y;}
  typedef T first_argument_type;
  typedef T second_argument_type;
  typedef T result_type;
};

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

Template parameters

T
Type of the arguments and return type of the functional call.
The type shall support the operation (operator*).

Member types

member typedefinitionnotes
first_argument_typeTType of the first argument in member operator()
second_argument_typeTType of the second argument in member operator()
result_typeTType returned by member operator()

Member functions

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

Example

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// factorials (multiplies example)
#include <iostream>     // std::cout
#include <functional>   // std::multiplies
#include <numeric>      // std::partial_sum

int main () {
  int numbers[9];
  int factorials[9];
  for (int i=0;i<9;i++) numbers[i]=i+1;
  std::partial_sum (numbers, numbers+9, factorials, std::multiplies<int>());
  for (int i=0; i<9; i++)
    std::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)