On Fri, 28 Jan 2005 22:10:21 -0500, Preston A. Elder wrote:
It also makes it easier for people writing custom parsers, since they can call the standard validation functions too. Notice, btw, how I made the instantiation of the validator static - this should save some cycles (not too many, but some) - by only ever creating one instance of the validator for each type in each function calling it - as opposed to creating an instance of the validator each time it is needed :)
Actually, a better idea would be to replace that 4th value (the 'long') and have instead the parser passed to the validate function, defaulting, of course, to validate_internal<T> (which uses lexical_cast). This way, if they want to define a new TYPE validator, specialize validate_internal<T>. If they want to define a different way to validate a specific type (ie. a parser), then create a new 'validator' - which basically is any function that has: template<typename charT> T operator()(const std::basic_string<charT> &s); defined (where T is the type to be returned - left as an exercise for the use to ensure that it is the same as T the validator is called with). so we end up with the validate function looking like: template<class T, class charT> validate(boost::any &v, const std::vector<std::basic_string<charT> >& xs), T *, const boost::function1<T, const std::basic_string<charT> &> &parser = validate_internal<T>()); You might be guessing where I'm going now. This makes the 'validate' functions basically only a way to differentiate between how data is stored (ie. as a value directly, as a vector of values, etc). The actual details of how to retrieve the data will then be completely left up to the parser, which could either be a specialization of validate_internal (or the default version using lexical_cast), a stand-alone function that returns the correct type, or any class that has an operator() accepting a (w)string and returns the correct type. As an added bonus then, the parser doesn't need to know whether its being stored in a vector, (as it currently does need to in my hacked up version). More food for thought. Meanwhile, I'm going to alter my hacked up version to do the above, and I'll post a link to the code when done :) -- PreZ :) Founder. The Neuromancy Society (http://www.neuromancy.net)