71 lines
2.7 KiB
C++
71 lines
2.7 KiB
C++
// fig14_16.cpp
|
|
// Demonstrating function objects.
|
|
#include <array>
|
|
#include <algorithm>
|
|
#include <functional>
|
|
#include <iostream>
|
|
#include <iterator>
|
|
#include <numeric>
|
|
|
|
// binary function returns the sum of its first argument total
|
|
// and the square of its second argument value
|
|
int sumSquares(int total, int value) {
|
|
return total + value * value;
|
|
}
|
|
|
|
// class SumSquaresClass defines overloaded operator()
|
|
// that returns the sum of its first argument total
|
|
// and the square of its second argument value
|
|
class SumSquaresClass {
|
|
public:
|
|
// add square of value to total and return result
|
|
int operator()(int total, int value) {
|
|
return total + value * value;
|
|
}
|
|
};
|
|
|
|
int main() {
|
|
std::array integers{1, 2, 3, 4};
|
|
std::ostream_iterator<int> output{std::cout, " "};
|
|
|
|
std::cout << "array integers contains: ";
|
|
std::ranges::copy(integers, output);
|
|
|
|
// calculate sum of squares of elements of array integers
|
|
// using binary function sumSquares
|
|
int result{std::accumulate(integers.cbegin(), integers.cend(),
|
|
0, sumSquares)};
|
|
|
|
std::cout << "\n\nSum of squares\n"
|
|
<< "via binary function sumSquares: " << result;
|
|
|
|
// calculate sum of squares of elements of array integers
|
|
// using binary function object
|
|
result = std::accumulate(integers.cbegin(), integers.cend(),
|
|
0, SumSquaresClass{});
|
|
|
|
std::cout << "\nvia a SumSquaresClass function object: " << result;
|
|
|
|
// calculate sum of squares array
|
|
result = std::accumulate(integers.cbegin(), integers.cend(),
|
|
0, [](auto total, auto value) {return total + value * value; });
|
|
|
|
std::cout << "\nvia a lambda: " << result << "\n";
|
|
}
|
|
|
|
|
|
/**************************************************************************
|
|
* (C) Copyright 1992-2021 by Deitel & Associates, Inc. and *
|
|
* Pearson Education, Inc. 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. *
|
|
**************************************************************************/
|