C++23 Features

The C++23 standard modernizes the language, introducing monadic error handling via std::expected, faster output streams via std::print, and explicit object parameters.

Monadic Error Handling: std::expected

Traditionally, APIs handle errors by returning codes or throwing exceptions. std::expected<T, E> provides a modern alternative: it holds a valid value of type T or an error details object of type E.

This allows you to write clean error-handling logic without throwing exceptions or checking magic return codes.

Code Walkthrough

Demonstrates using std::expected for error handling and explicit object parameters in C++23.

#include <iostream>
#include <expected>
#include <string>
#include <print> // C++23: print headers
enum class ParseError { InvalidChar, EmptyInput };
// C++23 expected: returns integer value or ParseError code
std::expected<int, ParseError> parseNumber(const std::string& str) {
    if (str.empty()) return std::unexpected(ParseError::EmptyInput);
for (char c : str) {
        if (c < '0' || c > '9') return std::unexpected(ParseError::InvalidChar);
    }
    return std::stoi(str);
}
class Widget {
public:
    // C++23 Deducing this: explicit object parameter
    template <typename Self>
    void log(this Self&& self) {
        std::println("Widget processed."); // Prints formatted string with newline
    }
};
int main() {
    auto res = parseNumber("12a4");
    if (!res) {
        if (res.error() == ParseError::InvalidChar) {
            std::println(stderr, "Error: Input contains invalid characters.");
        }
    } else {
        std::println("Parsed value: {}", *res);
    }
Widget w;
    w.log(); // Implicitly passes object pointer via deducing this
return 0;
}

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