Re: [Opencxx-users] opencxx refactoring

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

Gilles J. Seguin wrote:
[...]
> 
> Templates make a C++ parser at least 'x' times harder.
> Can you explain how we can handle template specialization with current
> parser.

Almost none in HEAD (there is some code in 'exp_templates' branch, but 
dated and perhaps it is not worth dragging in).

> What I understand,
> - specializing templates requires that the tokens for a template
>   declaration be saved so that the template can be reprocessed when the
>   actual template arguments are specified.

More than that. Types in template definition that do not depend on 
template arguments must be bound in the point of definition; remaining 
types are bound in the point of instantiation. This means, that either 
you have to bind the types after you read the definition or you need to 
store the environment "snapshot" from the point of definition, to be 
able to bind appropriately at the point of instantiation.

> - it requires the syntax phase to perform near-complete type, scope, and
>   expression analysis, including function overloading.

Not really.

First of all, if you just want to *parse*, then parser does have to 
perform all this analysis; for parser it is enough to know if a given 
identifier denotes template or not.

Second, even if you want to perform all this analysis during parsing, 
you don't have to (and IMO you should not) put the implementation into 
parser. The design I am suggesting is that Parser stores a pointer to
AbstractStaticAnalyzer. AbstractStaticAnalyzer is an interface that 
Parser uses to inform the rest of the system, that it parsed certain 
constructs. The implementation of AbstractStaticAnalyzer may, based on 
the information from Parser, maintain the data structures such as 
representations of scopes, classes or templates. However, another 
implementation of AbstractStaticAnalyzer may just do nothing, and it can 
be used for testing or in applications that are not concerned with full 
templates processing (e.g. pretty-printer).

> Present design predate such change to the language.
> In my vocabulary, present design is "C-Front style".

That's right.

> So my believed is that we need to rejuvenate the design.
> But my question is how.

Let me know if the description above makes sense for you.

BR
Grzegorz