[Opencxx-users] Re: [opencxx] Let's break OpenC++ up

[Grzegorz J. <ja...@he...>]

On Mon, 14 Apr 2003, James Michael DuPont wrote:

[...]
> 1. the preprocessor
> 2. the lexer
> 3. the yacc
> 4. the trees (ast in gcc)
> 5. the rtl (in gcc)
> 6. the debug information(in gcc)
>
> All of these are just producing messages.
> we need to have a callback filtering system so that the user can
> register and subscribe to get the information needed. That will
> predicate a identifier system that allows addressing of any part of the
> system with an identifier.
>
> This query system could be just a set of callbacks, each callback would
> be a differnet type of function.
>
> of course that could be made into a set of classes with methods you can
> override. Maybe even a generic function that would allow you to get a
> fully instanciated object of a given type.

In the framework I have in mind there is no callback registration.
The user of the framework supplies an object whose type is a class with
overloaded operator(). Overloads are distinguished based on the
kind of nodes in the tree. Kinds of nodes can be just nodes types,
but not necessarily --- one kind can be implemented by many types
and vice versa. The framework takes tree node implementation, decides
what kind is it and calls the appropriate overload on user-supplied
object.

> The treecc is good for defining all the types of nodes. the question of
> limiting the view and scope of data is a separate one.

I do not think that there is the universal set of types of nodes, perhaps
cons/nil is the only common denominator. It is very much domain dependent
and the framewok should not fix it. Take a look at SLT, which defines just
requirements on types (concepts) of containers. STL algorithms can be used
with any types, not only the ones defined in STL (standard containers'
iterators). For an example: imagine somebody prepared universal set of nodes
for C++ before Chiba invented OpenC++. Now comes Chiba and wants to have
some nodes which represent arbitrary chunks of text inserted into C++ parse
tree. It is very unlikely, that the person who focused on inventing
"universal" C++ parse tree predicted Chiba's requirement. We are in similar
situation.

Thanks for your input.
Grzegorz

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