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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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