57 lines
2.3 KiB
C++
57 lines
2.3 KiB
C++
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// fig15_14.cpp
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// Variadic function templates.
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#include <fmt/format.h>
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#include <iostream>
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#include <string>
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// base-case function for one argument
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template <typename T>
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auto sum(T item) {
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return item;
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}
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// recursively add one or more arguments
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template <typename FirstItem, typename... RemainingItems>
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auto sum(FirstItem first, RemainingItems... theRest) {
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return first + sum(theRest...); // expand parameter pack for next call
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}
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// add one or more arguments with a fold expression
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template <typename FirstItem, typename... RemainingItems>
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auto foldingSum(FirstItem first, RemainingItems... theRest) {
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return (first + ... + theRest); // expand the parameter
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}
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int main() {
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using namespace std::literals;
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std::cout << "Recursive variadic function template sum:"
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<< fmt::format("\n{}{}\n{}{}\n{}{}\n{}{}\n\n",
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"sum(1): ", sum(1), "sum(1, 2): ", sum(1, 2),
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"sum(1, 2, 3): ", sum(1, 2, 3),
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"sum(\"s\"s, \"u\"s, \"m\"s): ", sum("s"s, "u"s, "m"s));
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std::cout << "Variadic function template foldingSum:"
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<< fmt::format("\n{}{}\n{}{}\n{}{}\n{}{}\n",
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"sum(1): ", foldingSum(1), "sum(1, 2): ", foldingSum(1, 2),
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"sum(1, 2, 3): ", foldingSum(1, 2, 3),
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"sum(\"s\"s, \"u\"s, \"m\"s): ",
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foldingSum("s"s, "u"s, "m"s));
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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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