[antlr-interest] Re: aspectANTLR sketch
lgcraymer
lgc at mail1.jpl.nasa.gov
Thu Jun 20 00:18:40 PDT 2002
--- In antlr-interest at y..., mzukowski at y... wrote:
> Do you see any validity to wanting to override a rule but not change
its
> syntax?
Monty--
If I interpret your question correctly (future orientation), then
there are only a few cases that I can think of. Tree structuring may
change, especially if calling rules are overridden. Actions may
change--different languages have different ideas of scoping, and
symbol table management changes accordingly (in theory, this should be
abstracted out by the developer; practice and theory don't always
match). In line expansion of called rules may be desirable to match
new semantics attached to a syntactic fragment (A B C has meaning, but
the encountered phrase is A B foo and foo might begin with a C;
therefore foo should be expanded inline). Replacement of calling (or
called) rules can introduce syntactic ambiguities, making it necessary
to add a syntactic predicate to a rule.
These cases would most likely arise from either building on a
less-than-perfect grammar or doing heavy-duty composition which draws
rules from multiple grammars to write a language processor for a "new"
language. Both of these situations would be good candidates for
refactoring and benefit from an IDE which included refactoring
support. [Of course, we would have to figure out what refactoring
patterns are desirable--iteration to recursion is obvious, as is rule
expansion, and restructurings which resolve ambiguities would be
useful; but I can think of others which I have difficulty describing.]
--Loring
> Monty
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