[antlr-interest] adding enum token types output for java target

[Gavin Lambert]

At 08:46 27/05/2008, Johannes Luber wrote:
 >enum is 1.5. It would be nice, if you could still add that to 
the
 >templates within comments, so targets with a support for enums 
can
 >simply change the output.

You could also make it an option, or an alternate target (like 
CSharp2).  Provided that Java supports nested classes (and I think 
it does), it's possible to build an enum-like class in the absence 
of explicit enum support.  (I did that in C++ once because I 
wanted the values to be scoped to the "enum" instead of floating 
in the parent class or global namespace.)  So the target code 
needn't change between the two.

The trouble with enums is that they're not extensible; you can't 
inherit from one and simply add a few extra values (which would be 
useful for adding imaginary tokens at the parser/treeparser 
level).  And since they can't be a base class the library code 
will still have to work with raw ints, which means a lot more 
casts will be required to type-juggle.  It gets messy very 
quickly.

You could get around this by using an enum-like-class for all 
targets (so you can have a common base in the library which the 
grammars inherit from), but then you have to create factory 
methods and possibly re-implement some of the reflection-like 
calls (since you won't be able to use the standard enum 
ones).  I'm not sure it's worth it.