[cedet-semantic] Re: Moving to Semantic 2.0 & %start nonterminal that generate multiple tags.

[Joseph K. <ki...@ac...>]

Hello again Eric,

"Eric M. Ludlam" <er...@si...> writes:

>>>> Joseph Kiniry <ki...@ac...> seems to think that:
>   [ ... ]
>>I've begun testing my grammar with CVS HEAD today and things look
>>good so far.
>
> Yay!

Right-on.

>>I'm now generating good looking sets of tags, but my current problem
>>is one of structure.  It is just the standard loosly-typed Lispisms;
>>things like something should be a list of lists, but I only have a
>>list, etc.
>>
>>Here is a problem that has come up though that I must ask about.
>>
>>I have top-level constructs that have multiple meanings.  For example,
>>a PVS datatype is a datatype, a type, and a function.  Unfortunately,
>>a top-level %start rule can only return a *single* tag, whereas I
>>would like to return a list of tags.
>
> I had identified that if I iterate in code over the same rule to
> generate the tags, it was more robust that using typical looping via
> recursive grammar rules.  This is how I can identify unmatched syntax.

I understand this choice.

> The assumption was that a give call into the parser would then return
> only one tag.
>
>>E.g.,
>>datatype : id theoryformals_opt COLON datatype_or_codatatype with_subtypes_ids_opt
>>           BEGIN
>>           importing_semicolon_opt
>>           assumingpart_opt
>>           datatypepart
>>           END id
>>           (list
>>            (TYPE-TAG $1 $4 (append $7 $8 $9) nil)
>>            (when $2
>>               (FUNCTION-TAG $1 $1 $2))
>>            (TAG $1 'datatype (append $7 $8 $9)))
>>         ;
>>
>>Any ideas on how to handle this problem?
>   [ ... ]
>
> I think I would return a tag of a new class.  Give it a name specific
> to your language.
>
> Then implement a function for `semantic-tag-expand-function'.  When
> it sees a tag of that new class, it will replace it with two or more
> new tags.
>
> If the function part of your declaration is a constructor, don't
> forget to set the attribute :constructor to non-nil.
>
> Hmmm.  I think it is the symbol `constructor' without the :.  I should
> fix that.
>
> Anyway, that is the official way to do that, and is used in C and
> Java for statements like this:
>
> int a, b;

Must (sub)functions of -expand-tag be written for all non-core
semantics tags, or only ones that are returned by %start denoted
rules?

In other words, were I to use custom tags on other, non-expand(full)
related production rules, would they would be expanded with my
semantic-tag-expand-function as well?  (I'm deep in refactor mode so I
cannot even compile my grammar at the moment, thus the silly
question.)

I don't see any discussion of semantic-tag-expand-function in the
current CVS head documentation (beyond an extremely brief mention in
the Semantic Tags chapter's Misc Tag Internals subsection), FWIW.

I've been updating the docs a bit in my local sandbox, fixing typos,
spelling errors, grammar, and clarifying issues.  Shall I send a diff
eventually to someone?

Joe
-- 
Joseph R. Kiniry                    ID 78860581      ICQ 4344804 
SOS Group, University of Nijmegen  http://www.cs.kun.nl/~kiniry/
KindSoftware, LLC                   http://www.kindsoftware.com/
Board Chair: NICE                    http://www.eiffel-nice.org/