negate


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

Negative function object class

This class defines function objects for the negative 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.

negate has its operator() member defined such that it returns the same value with the opposite sign (i.e., its negation).

This class is derived from unary_function and is defined as:

1
2
3
4
 
template <class T> struct negate : unary_function <T,T> {
  T operator() (const T& x) const
    {return -x;}
};


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

Members

T operator() (const T& x)
Member function returning -x.


Example

1
2
3
4
5
6
7
8
9
10
11
12
13
 
// negate example
#include <iostream>
#include <functional>
#include <algorithm>
using namespace std;

int main () {
  int numbers[]={10,-20,30,-40,50};
  transform ( numbers, numbers+5, numbers, negate<int>() );
  for (int i=0; i<5; i++)
	  cout << numbers[i] << " ";
  return 0;
}


Output:

-10 20 -30 40 -50


See also

plus Addition function object class (class template)
minus Subtraction function object class (class template)
multiplies Multiplication function object class (class template)
divides Division function object class (class template)
modulus Modulus function object class (class template)
equal_to Function object class for equality comparison (class template)
unary_function Unary function object base class (class template)