template <class T> struct negate;

<functional>

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:

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

// 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