// 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));
}


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