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C & C++ Multimedia Cyber Classroom
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C and C++ Multimedia Cyber Classroom (Prentice Hall) (1998).iso
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src
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fig20_42.jar
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Ch20
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Fig20_42
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fig20_42.cpp
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C/C++ Source or Header
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1997-11-12
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2KB
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49 lines
// Fig. 20.42: fig20_42.cpp
// Demonstrating function objects.
#include <iostream>
#include <vector>
#include <algorithm>
#include <numeric>
#include <functional>
using namespace std;
// binary function adds the square of its second argument and
// the running total in its first argument and
// returns the sum
int sumSquares( int total, int value )
{ return total + value * value; }
// binary function class template which defines an overloaded
// operator() that function adds the square of its second
// argument and the running total in its first argument and
// returns the sum
template< class T >
class SumSquaresClass : public binary_function< T, T, T >
{
public:
const T &operator()( const T &total, const T &value )
{ return total + value * value; }
};
int main()
{
const int SIZE = 10;
int a1[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
vector< int > v( a1, a1 + SIZE );
ostream_iterator< int > output( cout, " " );
int result = 0;
cout << "vector v contains:\n";
copy( v.begin(), v.end(), output );
result = accumulate( v.begin(), v.end(), 0, sumSquares );
cout << "\n\nSum of squares of elements in vector v using "
<< "binary\nfunction sumSquares: " << result;
result = accumulate( v.begin(), v.end(), 0,
SumSquaresClass< int >() );
cout << "\n\nSum of squares of elements in vector v using "
<< "binary\nfunction object of type "
<< "SumSquaresClass< int >: " << result << endl;
return 0;
}