57 lines
2.4 KiB
C++
57 lines
2.4 KiB
C++
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// fig15_08.cpp
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// Using concepts to select overloads.
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#include <array>
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#include <iostream>
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#include <iterator>
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#include <list>
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// calculate the distance (number of items) between two iterators
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// using input iterators; requires incrementing between iterators,
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// so this is an O(n) operation
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template <std::input_iterator Iterator>
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auto customDistance(Iterator begin, Iterator end) {
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std::cout << "Called customDistance with input iterators\n";
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std::ptrdiff_t count{0};
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// increment from begin to end and count number of iterations
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for (auto& iter{begin}; iter != end; ++iter) {
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++count;
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}
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return count;
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}
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// calculate the distance (number of items) between two iterators
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// using random-access iterators and an O(1) operation
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template <std::random_access_iterator Iterator>
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auto customDistance(Iterator begin, Iterator end) {
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std::cout << "Called customDistance with random-access iterators\n";
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return end - begin; // returns a std::ptrdiff_t value
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}
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int main() {
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std::array ints1{1, 2, 3, 4, 5}; // has random-access iterators
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std::list ints2{1, 2, 3}; // has bidirectional iterators
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auto result1{customDistance(ints1.begin(), ints1.end())};
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std::cout << "ints1 number of elements: " << result1 << "\n";
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auto result2{customDistance(ints2.begin(), ints2.end())};
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std::cout << "ints2 number of elements: " << result2 << "\n";
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}
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/**************************************************************************
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* (C) Copyright 1992-2022 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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