[antlr-interest] new action syntax proposal
Kay Roepke
kroepke at classdump.org
Fri Jul 13 16:51:50 PDT 2007
On Jul 14, 2007, at 1:40 AM, Terence Parr wrote:
> Actions are not executed during backtracking as we cannot undo
> stateful actions. The problem is that some semantic predicates
> that test, for example, the symbol table rely on actions updating
> the symbol table during backtracking. I propose {...} stay same as
> an action but {{...}} (double curlies) implies always execute even
> when backtracking.
I suppose this is a bit paranoid, but in most languages we target the
curlies are the block delimiters. There's a minimal chance that
someone writes double curlies to introduce a different automatic
scope in the C-based targets. (this notion of automatic vars doesn't
really apply to Java, right? There was something with everything
being set up on method entry, IIRC. Don't quote me on this, though.)
If that happens, the semantics would change, probably without the
grammar author noticing. And we couldn't even issue a warning because
that warning would be totally silly for like 99.99999% of the users.
I don't have a better idea for the tokens, just came across my mind
when reading it.
cheers,
-k
--
Kay Röpke
http://classdump.org/
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