Re: [boost] RFC: Boost.XML API prototype in the sandbox -> generation form xsd

From: Oliver.Kowalke_at_[hidden]
Date: 2007-07-12 04:06:22

> > You are forced to validate it at runtime.
> 
> Nothing's really new here.  You can't validate XML at compile time. 
> Unless you mean something different.

please see below

> > Phils suggestion is more typesafe:
> 
> No, it's just more verbose, and there's no way to eliminate 
> all the intermediate variables.
> 
> Type is enforced only by the structure of the data and the 
> way that it's interpreted by the parser/writer.  You may as 
> well pick an interface that just lets you read/write 
> hierarchical data easily, or support an extension that 
> already deals with interpretation, like schemas.
> 
> > articleinfo ai;
> > {
> >    if (title) ai.push_back(comment("This title was moved"));
> >    author a;
> >    {
> >      a.push_back(firstname("Joe"));
> >      a.push_back(surname("Random"));
> >      ai.push_back(a);
> >    }
> >    root.push_back(ai);
> > }
> 
> I don't really see how it's more type-safe.  The structures 
> "articleinfo", "firstname" and "surname" would all inherit 
> from "element", which is presumably a type accepted by 
> "push_back".  So nothing prevents you from doing:
> 
> root.push_back(firstname("Joe"));
> 
> which is exactly what you had hoped to avoid.
> 
> If you really want type-safety at this level, you'd have to 
> define a push_back for all the sub-element types accepted by 
> an element (and push_front, insert, etc.).  No thanks.

I would do it over templates - than it's type safe and a part of the xml
validation can be done at compile time.

typedef tag<
        mpl::vector< title, author >	// tags
        mpl::vector< isbn > // atributes
>	article_info;

etc.

Regards, Oliver