69 lines
2.9 KiB
C++
69 lines
2.9 KiB
C++
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// fig06_13.cpp
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// Functional-style programming with C++20 ranges and views.
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#include <array>
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#include <fmt/format.h>
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#include <iostream>
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#include <numeric>
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#include <ranges>
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int main() {
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// lambda to display results of range operations
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auto showValues{
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[](auto& values, const std::string& message) {
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std::cout << fmt::format("{}: ", message);
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for (const auto& value : values) {
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std::cout << fmt::format("{} ", value);
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}
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std::cout << '\n';
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}
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};
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auto values1{std::views::iota(1, 11)}; // generate integers 1-10
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showValues(values1, "Generate integers 1-10");
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// filter each value in values1, keeping only the even integers
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auto values2{values1 |
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std::views::filter([](const auto& x) {return x % 2 == 0;})};
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showValues(values2, "Filtering even integers");
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// map each value in values2 to its square
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auto values3{
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values2 | std::views::transform([](const auto& x) {return x * x;})};
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showValues(values3, "Mapping even integers to squares");
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// combine filter and transform to get squares of the even integers
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auto values4{
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values1 | std::views::filter([](const auto& x) {return x % 2 == 0;})
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| std::views::transform([](const auto& x) {return x * x; })};
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showValues(values4, "Squares of even integers");
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// total the squares of the even integers
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std::cout << fmt::format("Sum squares of even integers 2-10: {}\n",
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std::accumulate(std::begin(values4), std::end(values4), 0));
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// process a container's elements
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constexpr std::array numbers{1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
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auto values5{
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numbers | std::views::filter([](const auto& x) {return x % 2 == 0;})
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| std::views::transform([](const auto& x) {return x * x; })};
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showValues(values5, "Squares of even integers in array numbers");
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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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