c-resources/CPlusPlus20ForProgrammers-m.../examples/ch15/fig15_14.cpp

57 lines
2.3 KiB
C++
Raw Normal View History

2024-04-09 06:45:18 +00:00
// fig15_14.cpp
// Variadic function templates.
#include <fmt/format.h>
#include <iostream>
#include <string>
// base-case function for one argument
template <typename T>
auto sum(T item) {
return item;
}
// recursively add one or more arguments
template <typename FirstItem, typename... RemainingItems>
auto sum(FirstItem first, RemainingItems... theRest) {
return first + sum(theRest...); // expand parameter pack for next call
}
// add one or more arguments with a fold expression
template <typename FirstItem, typename... RemainingItems>
auto foldingSum(FirstItem first, RemainingItems... theRest) {
return (first + ... + theRest); // expand the parameter
}
int main() {
using namespace std::literals;
std::cout << "Recursive variadic function template sum:"
<< fmt::format("\n{}{}\n{}{}\n{}{}\n{}{}\n\n",
"sum(1): ", sum(1), "sum(1, 2): ", sum(1, 2),
"sum(1, 2, 3): ", sum(1, 2, 3),
"sum(\"s\"s, \"u\"s, \"m\"s): ", sum("s"s, "u"s, "m"s));
std::cout << "Variadic function template foldingSum:"
<< fmt::format("\n{}{}\n{}{}\n{}{}\n{}{}\n",
"sum(1): ", foldingSum(1), "sum(1, 2): ", foldingSum(1, 2),
"sum(1, 2, 3): ", foldingSum(1, 2, 3),
"sum(\"s\"s, \"u\"s, \"m\"s): ",
foldingSum("s"s, "u"s, "m"s));
}
/**************************************************************************
* (C) Copyright 1992-2022 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. *
**************************************************************************/