Re: Java Comment-Preserving Grammar

>
> Is there an available Java grammar which preserves comments in an
> output AST tree? I know there are plenty of java grammars out there,
> but all ignore comments. I'm happy to use any tool providing I can
> gain access to the comments in the tree.
>
> My end goal is to parse commented-out extensions to the java language:
>
> class /*#immutable*/ Blah {
>
> public /*#input*/ int x;
> public /*#result*/ int y;
>
> }


The parser generator suite I am most familiar with is Lex (flex) /
YACC (bison). The way I usually see /* comments handled there is
having the lexer go into new new state and ignoring everything until
*/. There are regular expressions to match the sequence, but it is too
easy to just use this approch. I imagine that most scanner generators
should have some analogous construct.


After the state change you can scan only the tokens you are interested in.
#input or #result.
You will probably want to switch your error handling strategys for this
state too.


Another suggestion is to extend in the comment begin delimiter.
Much like the javadocs will ignore /* and expects /**, you
could invent something like /*# (that may be your intention, but I cannot
tell).
You could state change to ignore /* and state change to only try and parse
/*# comments.


This is a neat idea.
Good luck,
- Tim

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