enumerable_default_if_empty2.cpp

Shows how to use xtd::linq::enumerable::default_if_empty method.

#include <xtd/xtd>
 
struct pet {
  string name;
  int age = 0;
  
  static pet default_pet;
  
  friend bool operator ==(const pet& lhs, const pet& rhs) noexcept {
    return lhs.name == rhs.name && lhs.age == rhs.age;
  }
};
 
pet pet::default_pet {.name = "Default pet", .age = 0};
 
auto main() -> int {
  auto pets1 = array<pet> {
    {.name="Barley", .age=8},
    {.name="Boots", .age=4},
    {.name="Whiskers", .age=1}
  };
  for (const auto& [name, age] : pets1.default_if_empty(pet::default_pet))
    console::write_line("pet {{name={}, age={}}}", name, age);
  console::write_line();
  
  auto pets2 = array<pet> {};
  for (const auto& [name, age] : pets2.default_if_empty(pet::default_pet))
    console::write_line("pet {{name={}, age={}}}", name, age);
  console::write_line();
}
 
// This code produces the following output :
//
// pet {name=Barley, age=8}
// pet {name=Boots, age=4}
// pet {name=Whiskers, age=1}
//
// pet {name=Default pet, age=0}
//