[antlr-interest] Reg Multi-line comments

[David-Sarah Hopwood]

Gokulakannan Somasundaram wrote:
> Actually there is a comment like this before the source code of the
> function.
> 
>     /** A more general version of getRuleInvocationStack where you can
>      *  pass in, for example, a RecognitionException to get it's rule
>      *  stack trace.  This routine is shared with all recognizers, hence,
>      *  static.
>      *
>      *  TODO: move to a utility class or something; weird having lexer call
>      *  this */
>     public static List getRuleInvocationStack(Throwable e,
>                                               String recognizerClassName)
> 
> 
> It more or less sounds to me that lexer should not call this.

The recipe in section 10.2 of 'The Definitive ANTLR Reference' does so,
therefore it's a supported API, not internal. Moving it would break all
lexers using that recipe.

Calling the static version of this method rather than the instance
version (with no arguments) is correct: if you don't obtain the stack
from the RecognitionException that is passed to getErrorMessage, then
the relevent lexer rule will no longer be on the current stack in some
cases.

> When i observe
> the source code, i see that your approach may not be possible, because the
> token to be tried out never gets saved anywhere. But let me check this.

It is possible because the implementation uses a stack trace to determine
which lexer methods were on the call stack when the RecognitionException
was thrown, and so no explicit state is needed. In any case, I tested this
code before posting; it works.

-- 
David-Sarah Hopwood  ⚥  http://davidsarah.livejournal.com