RE: 2 questions (...! and itempos) and 1 wish ('universal' action)

Damian,

Thanks!

Before 'universal' action becomes a feature, I'll find a way to simulate
that.

Eric

-----Original Message-----
From: Damian Conway [mailto:[email protected]]
Sent: Monday, September 10, 2001 1:27 AM
To: [email protected]; Eric Liao
Subject: Re: 2 questions (...! and itempos) and 1 wish ('universal'
action)


Hi Eric,

Sorry for the delay in replying...I am a victim of my own notoriety
nowadays
and my response time suffers accordingly :-(

You asked:

   > (1) The way the IDENT production is written does not accept
   > 'newgoodident' as a valid identifier because it starts with one of
the
   > keywords.  In reality, 'newgoodident' is a valid identifier, and
   > changing the rule from IDENT to IDENT2 gives the correct result
(change
   > 'Got $item[2]' to 'Got $item[1]' if you try IDENT2).  The problem
with
   > IDENT2, which uses negative lookbehind, is that the long list of
   > keywords is duplicated and is messy.  What did I do wrong with
IDENT?

Nothing. You messed up KEYWORD instead ;-)

What you meant was:

	KEYWORD:
	   /^(new|public)\b/

In other words, a keyword is 'new' or 'public'
with a word boundary immediately after it.
^^^^^^^^^^^^^^^^^^^^


   > (2) At the end of the grammar there's presence of commented-out
   > '@itempos'.  Strangely, I discovered that the presence of
'@itempos' or
   > at least '$itempos[' (with left square bracket) anywhere inside the
   > grammar, even if commented out, seems to be necessary for the
various
   > $itempos{...}{...} variables to be accessible from inside
AUTOACTION.
   > Without the presence, I got an error like this:
   > 
   >        ERROR: Internal error in generated parser code!
   >        (Hint: Global symbol "@itempos" requires explicit package
name
   >        at (eval 10) line 104, <DATA> line 1. Global symbol
   >        "@itempos" requires explicit package name at (eval 10)
   >        line 179, <DATA> line 1. BEGIN not safe after errors--
   >        compilation aborted at (eval 10) line 297, <DATA> line
   >        1. )
   > 
   > Can this be a bug?  Or is this because $itempos{...}{...} variables
are
   > designed to be used only in the actions of individual rules?  I
hope
   > not.  Or, please point out if I did anything wrong.

A bug. I overlooked the possibility of autoactions injecting @itempos
usages
when writing the code that decides whether to include @itempos
calculations
in a grammar. I've patched that now and credited you with its discovery.
You're comment is the appropriate workaround in the meantime.

   
   > (3) Wish to have: I realize that AUTOACTION is executed for a
matching
   > rule only when no action is defined for that rule.  But I ran into
   > situations where a universal kind of action would be useful (mostly
for
   > debugging purposes but where setting the TRACE flag seems
overkill).  By
   > 'universal' I mean an action that is executed for ALL matching
rules
   > regardless of whether individual action exists.  This 'universal'
action
   > can either precede or follow the execution of individual action.

I'll add that to the ToDo list.

Damian