[antlr-interest] header and extra code blocks in supergrammars

[Micheal J]

> Hi All,
> 
> I'm experimenting with splitting my TreeParser into a 
> supergrammar and several distinct subgrammars.  One annoyance 
> I'm running in to is that the subgrammars don't appear to 
> inherit the header block or the extra code block.  That means 
> I have to replicate those sections in each subgrammar, which 
> is a bit of a maintenance headache.
> 
> For the header section, I can get away with having the 
> subgrammar's include the supergrammar's header, but this 
> trick won't work for the extra code block because it gets 
> inserted into the cpp file.
> 
> Am I missing something?

Perhaps not. I've usually tackled this by instructing ANTLR to generate tree
parsers that derive from my own custom class (itself a
TreeParser-derivative). This takes care of the common code in the extra code
block since I can include all that in my custom base class.

ANTLR v2's "inheritance" feature is then used to ensure the right
rules/actions are generated for individual tree parsers.

As you say, the header stuff has to be repeated in each grammar but that's
not an issue really.

Micheal