std_expected

std::expected

Test out how errors might be used with this C++23 feature.

main.cc

make main
./main 5 8
./main 5 0

CLI dividing calculator. Uses std::expected to parse the CLI args and std::optional to handle divide by zero.

The CLI parse() method returns std::expected<Config, parse_error> where Config is a struct holding valid arguments and parse_error is an enum of possible errors. The error enum is passed to a switch statement to handle errors differently depending on their type.

This error handling method is rough equivalent to

Config parse(int argc, char* argv[]) {
    if(argc != 3) throw ParseErrorWrongNumber();
    float a, b;
    try {
        a = std::stof(argv[1]);
        b = std::stof(argv[2]),
    } catch (const std::invalid_argument& e) {
        throw ParseErrorInvalidArgument();
    }
    return Config{a, b};
}

int main(int argc, char* argv[]){
    try {
        Config config = parse(...);
    } catch (const ParseErrorWrongNumber& e) {
        // handle wrong number of args
    } catch (const ParseErrorInvalidFloat& e){
        // handle invalid arg
    }
}

rusty.cc

make rusty
./rusty

The rusty.h header file defines typedefs and functions to make C++ exceptions and optionals handle like Rust's Result and Option. I wrote match() statements for both types which resemble Rust's match, though imperfectly.