#include <iostream>

#include <expected>

using namespace std;

enum class error

{

compile_time_error,

runtime_error

};

auto unexpected_runtime_error() -> expected<int, error>

{

return unexpected(error::runtime_error);

}

int main(int argc, char* argv[])

{

expected<double, int> ex = unexpected(3);

if (!ex)

cout << "ex contains an error\n";

if (ex == unexpected(3))

cout << "The error value is equal to 3\n";

const auto e = unexpected_runtime_error();

e.and_then([](const auto& e) -> expected<int, error>

{

cout << "and_then" << int(e);

return {};

})

.or_else([](const auto& e) -> expected<int, error>

{

cout << "or_else: " << int(e);

return {};

});

return 0;

}