template <class T> struct logical_or;

<functional>

Logical OR function object class

This class defines function objects for the "or" logical 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.

logical_or has its operator() member defined such that it returns true if either (or both) of its arguments are true (using operator||), and false otherwise (when neither of the arguments is true).

This class is derived from binary_function and is defined as:

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

Objects of this class can be used with several standard algorithms (see algorithm).

Members

T operator() (const T& x, const T& y)

Member function returning the result of x||y.

Example

// logical_or example
#include <iostream>
#include <functional>
#include <algorithm>
using namespace std;

int main () {
  bool foo[] = {true,false,true,false};
  bool bar[] = {true,true,false,false};
  bool result[4];
  transform (foo, foo+4, bar, result, logical_or<bool>() );
  cout << boolalpha << "Logical OR:\n";
  for (int i=0; i<4; i++)
	  cout << foo[i] << " OR " << bar[i] << " = " << result[i] << "\n";
  return 0;
}

Output:

Logical OR:
true OR true = true
false OR true = true
true OR false = true
false OR false = false

See also