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// Fig. 21.42: fig21_42.cpp
// Demonstrating function objects.
#include <iostream>
using std::cout;
using std::endl;
#include <vector> // vector class-template definition
#include <algorithm> // copy algorithm
#include <numeric> // accumulate algorithm
#include <functional> // binary_function definition
// binary function adds square of its second argument and
// running total in its first argument, then returns sum
int sumSquares( int total, int value )
{
return total + value * value;
} // end function sumSquares
// binary function class template defines overloaded operator()
// that adds suare of its second argument and running total in
// its first argument, then returns sum
template< class T >
class SumSquaresClass : public std::binary_function< T, T, T > {
public:
// add square of value to total and return result
const T operator()( const T &total, const T &value )
{
return total + value * value;
} // end function operator()
}; // end class SumSquaresClass
int main()
{
const int SIZE = 10;
int array[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
std::vector< int > integers( array, array + SIZE );
std::ostream_iterator< int > output( cout, " " );
int result = 0;
cout << "vector v contains:\n";
std::copy( integers.begin(), integers.end(), output );
// calculate sum of squares of elements of vector integers
// using binary function sumSquares
result = std::accumulate( integers.begin(), integers.end(),
0, sumSquares );
cout << "\n\nSum of squares of elements in integers using "
<< "binary\nfunction sumSquares: " << result;
// calculate sum of squares of elements of vector integers
// using binary-function object
result = std::accumulate( integers.begin(), integers.end(),
0, SumSquaresClass< int >() );
cout << "\n\nSum of squares of elements in integers using "
<< "binary\nfunction object of type "
<< "SumSquaresClass< int >: " << result << endl;
return 0;
} // end main
/**************************************************************************
* (C) Copyright 1992-2003 by Deitel & Associates, Inc. and Prentice *
* Hall. All Rights Reserved. *
* *
* DISCLAIMER: The authors and publisher of this book have used their *
* best efforts in preparing the book. These efforts include the *
* development, research, and testing of the theories and programs *
* to determine their effectiveness. The authors and publisher make *
* no warranty of any kind, expressed or implied, with regard to these *
* programs or to the documentation contained in these books. The authors *
* and publisher shall not be liable in any event for incidental or *
* consequential damages in connection with, or arising out of, the *
* furnishing, performance, or use of these programs. *
*************************************************************************/
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