set_nargs()

Rationale

This method allows you to set how many values are expected for an argument.

Possible values

You may specify as an argument to this function one of the following values:

• x -> any integer number
• * -> which means at zero or more values
• + -> which means at least one or more values

Example usage

parser.add_argument("files").set_nargs('*');

Source Code

Arg &set_nargs(const auto nargs)
{
    static constexpr auto is_number = std::is_same_v<decltype(nargs), const int>;
    static constexpr auto is_symbol = std::is_same_v<decltype(nargs), const char>;

    if constexpr (is_number) {
        this->nargs = nargs;
    } else if constexpr (is_symbol) {
        this->nargs = nargs - '0';
    } else {
        throw exceptions::ArgparseException(
            std::source_location::current(),
            "set_nargs() error: unsupported type: %\nSupported types are: int, std::string\n",
            typeid(nargs).name());
    }

    return *this;
}

Moreover the function uses C++17 if constexpr to generate at compile time the right branch of the if statement, reducing the overhead during runtime.

Note: Be aware that the function will throw an exception if the argument is not a number or one of the supported symbols symbol.