[antlr-interest] MismatchedTokenException and how to find errors in ANTLRWorks

[Matt Benson]

--- Gavin Lambert <antlr at mirality.co.nz> wrote:

> At 08:39 13/02/2008, Matt Benson wrote:
>  >Seriously, Jim:  what's the likelihood of your (or
>  >anyone's) being able to sum up the reason for this
>  >fairly succinctly?  What is the #1 gotcha about
> using
>  >literals vs. tokens that ANTLR3 beginners
> overlook?
> 
> I gave my answer to that question yesterday (though
> more 
> briefly).  As I see it, there are two big drawbacks
> to using 
> literal strings in the parser:
> 
> 1. The generated code becomes filled with references
> to "T32" and 
> "T63" etc rather than anything meaningful, making it
> harder to 
> understand.  (And also complicating things if you
> want to generate 
> an AST later on.)
> 
> 2. It's too easy to forget that each quoted string
> produces a 
> lexer rule (which may conflict with other rules),
> making it harder 
> to find the source of ambiguity problems.  In
> addition, "'x' 'y'" 
> is not the same as "'xy'" in the parser, though it
> is in the 
> lexer; this can cause confusion.
> 
> 

Thanks, Gavin.  Now flip the coin:  what, if anything,
is _good_ about literals in the parser outside of a
rapid prototyping context?

-Matt


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