[antlr-interest] Possible Antlr defect?

Gavin Lambert antlr at mirality.co.nz
Sat Jun 9 20:16:13 PDT 2007


At 13:08 10/06/2007, Terence Parr wrote:
 >
 >Yep.  It is vulnerable to typos, but only comes up when you're
 >building separate parser and lexer (or a tree parser I guess).

As with any compiled language, I think it's far better to require 
declaration before use to prevent this sort of problem.  It's 
trivial to declare any fake tokens required in a "tokens" block, 
so the cost of requiring predeclaration is (in my opinion) vastly 
less than the cost of *not* requiring predeclaration, where you 
spend hours of pain and torment trying to figure out why something 
isn't working, finally noticing a simple misspelling or 
transposition error.  (And yes, I've had that happen to me before 
with other [usually interpreted] languages that didn't enforce 
predeclaration, so I know whereof I speak.)

 >I think ANTLRWorks puts a red squiggly line underneath if it
 >is not defined.  I will have to check.

It does, at least in the combined grammar case (I haven't tested 
the imported vocab case).



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