71 lines
2.7 KiB
C++
71 lines
2.7 KiB
C++
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// fig14_16.cpp
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// Demonstrating function objects.
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#include <array>
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#include <algorithm>
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#include <functional>
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#include <iostream>
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#include <iterator>
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#include <numeric>
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// binary function returns the sum of its first argument total
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// and the square of its second argument value
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int sumSquares(int total, int value) {
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return total + value * value;
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}
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// class SumSquaresClass defines overloaded operator()
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// that returns the sum of its first argument total
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// and the square of its second argument value
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class SumSquaresClass {
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public:
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// add square of value to total and return result
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int operator()(int total, int value) {
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return total + value * value;
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}
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};
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int main() {
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std::array integers{1, 2, 3, 4};
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std::ostream_iterator<int> output{std::cout, " "};
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std::cout << "array integers contains: ";
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std::ranges::copy(integers, output);
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// calculate sum of squares of elements of array integers
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// using binary function sumSquares
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int result{std::accumulate(integers.cbegin(), integers.cend(),
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0, sumSquares)};
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std::cout << "\n\nSum of squares\n"
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<< "via binary function sumSquares: " << result;
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// calculate sum of squares of elements of array integers
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// using binary function object
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result = std::accumulate(integers.cbegin(), integers.cend(),
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0, SumSquaresClass{});
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std::cout << "\nvia a SumSquaresClass function object: " << result;
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// calculate sum of squares array
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result = std::accumulate(integers.cbegin(), integers.cend(),
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0, [](auto total, auto value) {return total + value * value; });
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std::cout << "\nvia a lambda: " << result << "\n";
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}
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/**************************************************************************
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* (C) Copyright 1992-2021 by Deitel & Associates, Inc. and *
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* Pearson Education, Inc. All Rights Reserved. *
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* *
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* DISCLAIMER: The authors and publisher of this book have used their *
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* best efforts in preparing the book. These efforts include the *
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* development, research, and testing of the theories and programs *
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* to determine their effectiveness. The authors and publisher make *
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* no warranty of any kind, expressed or implied, with regard to these *
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* programs or to the documentation contained in these books. The authors *
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* and publisher shall not be liable in any event for incidental or *
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* consequential damages in connection with, or arising out of, the *
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* furnishing, performance, or use of these programs. *
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**************************************************************************/
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