class template
<functional>

std::negate

template <class T> struct negate;
Negative function object class
Unary function object class whose call returns the result of negating its argument (as returned by the unary operator -).

Negating a value returns the same value with the opposite sign.

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 negate : unary_function <T,T> {
  T operator() (const T& x) const {return -x;}
};

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template <class T> struct negate {
  T operator() (const T& x) const {return -x;}
  typedef T argument_type;
  typedef T result_type;
};


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

Template parameters

T
Type of the argument and return type of the functional call.
The type shall support the operation (unary operator-).

Member types

member typedefinitionnotes
argument_typeTType of the argument in member operator()
result_typeboolType returned by member operator()

Member functions

T operator() (const T& x)
Member function returning the negation of its argument (-x).

Example

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// negate example
#include <iostream>     // std::cout
#include <functional>   // std::negate
#include <algorithm>    // std::transform

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

C++