cpp

    
template<class U>
expected(const expected<U, E>& other) : _has_value(other.has_value())   // a copy constructor  
{
        if (_has_value)
        {
                if constexpr (std::is_same<U, monostate>::value) // it checks if U == monostate
                {
                        // makes an empty instance of "T"
                }
                else if constexpr (std::is_same<U, T>::value) // it checks if U == T
                {
                        // otherwise copies "other._value" into _value
                }
                else
                {
                        static_assert(
                            not std::is_same<U, T>::value, "no available conversion between the provided value types");
                }
        }
        else
        {
                new (std::addressof(_error)) E(other.error());
        }
}

 template<class E>
 expected<monostate, E> unexpected(const E& e) // then this can covert <monostate, E> to <T, E> fine because of this copy constructor
 {                
         return expected<monostate, E>(e);
 }


// example usage

nl::expected<int, std::string> meow = nl::unexpected("error");

  

 cpp

    
expected(const expected<monostate, E>& other)


  

 cpp

    
expected(const expected& other)

  

 cpp

    
std::map<std::string, int> obj = {{"a", 1}, {"b", 2}};
std::vector<std::string> arr = {"x", "y", "z"};
ljson::node data;
data.insert("object", obj);
data.insert("array", arr);

  

 cpp

    
ljson::node n = {
    {"name", "Alice"},
    {"age", 30},
    {"active", true},
    {"tags", ljson::node({"dev", "cat_lover"})},
    {"profile", ljson::node({{"city", "Paris"}, {"zip", 75000}})}
};
// n is now a JSON object with nested objects and arrays!

  

 cpp

    
if (n.at("age").is_integer())
    std::cout << "Age: " << n.at("age").as_integer() << "\n";
if (n.at("tags").is_array()) {
    for (auto& tag : *n.at("tags").as_array())
        std::cout << tag.as_string() << " ";
}

  

 cpp

    
n.at("name") = "Bob";      // changes value to "Bob"
n.at("age")  = 31;         // changes value to 31
n.at("active") = false;    // changes value to false
n.at("tags").push_back("gamer"); // add "gamer" to tags array

  

 cpp

    
auto result = ljson::parser::try_parse(R"({"x":1})");
if (result) {
    std::cout << "Parsed!\n";
} else {
    std::cerr << "Parse error: " << result.error().message() << "\n";
}

  

 cpp

    
n.dump_to_stdout({'\t', 2});         // Pretty print using tabs, 2 per indent
n.write_to_file("output.json");       // Write to file
std::string s = n.dump_to_string();   // Get pretty JSON string

  

 cpp

    
ljson::node a = {1, 2, 3};
ljson::node b = {4, 5};
ljson::node c = a + b; // [1,2,3,4,5]

ljson::node obj1 = {{"x", 1}};
ljson::node obj2 = {{"y", 2}};
ljson::node obj3 = obj1 + obj2; // {"x":1,"y":2}


  

 cpp

    
n.insert("nothing", ljson::null);
if (n.at("nothing").is_null())
    std::cout << "It's " << n.at("nothing").stringify() << "!\n"; // It's null!

  

 cpp

    
ljson::node arr = { 1, 2, 3, ljson::node({"nested", "array"}), ljson::null };
ljson::node obj = { {"a", 1}, {"b", ljson::node({2, 3, 4})}, {"c", ljson::node({"d", 5})} };

  

 cpp

    
n.at("val").set(123.45);
n.at("flag") = true;
n.at("sub").insert("newkey", "newval");

  

 cpp

    
// Iterating an array
for (auto& item : *n.at("tags").as_array())
    std::cout << item.as_string() << "\n";

// Iterating an object
for (auto& [key, value] : *n.as_object())
    std::cout << key << ": " << value.stringify() << "\n";

  

 cpp

    
auto res = n.at("name").try_as_integer();
if (!res) std::cerr << "Not an integer: " << res.error().message() << "\n";

  

 cpp

    
n.dump_to_stdout({' ', 8}); // 8 spaces per indent

  

 cpp

    
ljson::node obj = {
    {"a", 1},
    {"b", 2}
};
obj += ljson::object_pairs{
    {"c", 3},
    {"d", 4}
};

  

 cpp

    
// accessing values in ljson
ljson::node node = ljson::parser::parse(raw_json);
std::string val = node.at("key").as_string();

// accessing values in nlohmann
nlohmann::json::json json;
raw_json >> json;
std::string val = json["key"].get<std::string>();