// fig15_15.cpp
// Unary fold expressions.
#include <fmt/format.h> 
#include <iostream>

template <typename... Items>
auto unaryLeftAdd(Items... items) {
   return (... + items); // unary left fold
}

template <typename... Items>
auto unaryRightAdd(Items... items) {
   return (items + ...); // unary right fold
}

template <typename... Items>
auto unaryLeftSubtract(Items... items) {
   return (... - items); // unary left fold
}

template <typename... Items>
auto unaryRightSubtract(Items... items) {
   return (items - ...); // unary right fold
}

int main() {
   std::cout << "Unary left and right fold with addition:"
      << fmt::format("\n{}{}\n{}{}\n\n",
         "unaryLeftAdd(1, 2, 3, 4): ", unaryLeftAdd(1, 2, 3, 4),
         "unaryRightAdd(1, 2, 3, 4): ", unaryRightAdd(1, 2, 3, 4));

   std::cout << "Unary left and right fold with subtraction:"
      << fmt::format("\n{}{}\n{}{}\n",
         "unaryLeftSubtract(1, 2, 3, 4): ",
         unaryLeftSubtract(1, 2, 3, 4),
         "unaryRightSubtract(1, 2, 3, 4): ",
         unaryRightSubtract(1, 2, 3, 4));
}


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