Validator from min to max.

[joshuak94]

Currently, if I have an option where I would like to accept any positive non-zero double value, I use

    sharg::arithmetic_range_validator dbl_val{0.0, std::numeric_limits<double>::max()};

However, in the help page it shows up like so:

    -j, --reThreshold (double)
          SVs satisfy read-depth evidence >= {Q3 + (IQR * h)} get a vote. Default: 1. Value must be in range
          [0.000000,179769313486231570814527423731704356798070567525844996598917476803157260780028538760589558632766878171540458953514382464234321326889464182768467546703537516986049910576551282076245490090389328944075868508455133942304583236903222948165808559332123348274797826204144723168738177180919299881250404026184124858368.000000].

This is pretty unsightly... Is there a way the readability can be improved somehow?

[eseiler]

You can just write your own validator:

class positive_double_validator
{
public:
    using option_value_type = double;

    positive_double_validator() = default;
    positive_double_validator(positive_double_validator const &) = default;
    positive_double_validator & operator=(positive_double_validator const &) = default;
    positive_double_validator(positive_double_validator &&) = default;
    positive_double_validator & operator=(positive_double_validator &&) = default;
    ~positive_double_validator() = default;

    void operator()(option_value_type const & val) const
    {
        if (val < 0.0)
            throw sharg::validation_error{"The value must be a positive double."};
    }

    std::string get_help_page_message() const
    {
        return "Value must be a positive double.";
    }
};

[eseiler]

You could also inherit, and only overwrite the help page message:

class positive_double_validator : public sharg::arithmetic_range_validator<double>
{
private:
    using base_t = sharg::arithmetic_range_validator<double>;

public:
    using base_t::base_t;
    // using base_t::option_value_type; // Didn't test - maybe needed
    // using base_t::operator();        // Didn't test - maybe needed

    positive_double_validator() = default;
    positive_double_validator(positive_double_validator const &) = default;
    positive_double_validator & operator=(positive_double_validator const &) = default;
    positive_double_validator(positive_double_validator &&) = default;
    positive_double_validator & operator=(positive_double_validator &&) = default;
    ~positive_double_validator() = default;

    std::string get_help_page_message() const
    {
        return "Value must be a positive double.";
    }
};

But the parser will already check that it can parse the double, so it doesn't help to check for numeric_limits<double>::max().

[joshuak94]

Ahh I see. So if I just wanted a double without caring about the values given, I could do
sharg::arithmetic_range_validator<double>{} in the sharg::config?

[eseiler]

If you don't care about the value, you don't need a validator at all. The parser will throw an error if it can't parse whatever was given as a double.
E.g., if a value is uint8_t, but you pass 1000, it will throw, even when there is no validator.

[joshuak94]

Right that makes sense.

[eseiler]

Yeah, but I think it's a bit confusing. I used to do the same, and use the range validator to check for valid input. Maybe the use case for arithmetic_range_validator isn't clear enough. Also, a cookbook entry for "I want my input to be positive" wouldn't hurt, because the range validator is a bit overkill for that.
A good use case for the range validator is, e.g., a k-mer size parameter, which needs to be in [1,32].