[antlr-interest] OPEN, EOF ambiguity

Cameron Ross cross at kojeware.com
Thu Apr 8 13:11:02 PDT 2010


Yes, this is the way I have it implemented in my production version.
 However, I have to conform to a language specification which allows text to
have zero or more phrases.  Is there some ANLTR magic that I can use to
support this?


On Thu, Apr 8, 2010 at 4:07 PM, Jim Idle <jimi at temporal-wave.com> wrote:

> Your text rule can be empty, you need to rejig your use of + and * or you
> end up with the empty match in more than one place.
>
>
>
> Jim
>
>
>
> From: Cameron Ross [mailto:cross at kojeware.com]
> Sent: Thursday, April 08, 2010 1:05 PM
> To: Jim Idle
> Subject: Re: [antlr-interest] OPEN, EOF ambiguity
>
>
>
> These rules give the gist of it...
>
>
>
> start_rule
>
>          : clif_file EOF
>
>          ;
>
>
>
> clif_file
>
>          : cltext+
>
>          ;
>
>
>
> cltext
>
>          : (OPEN CL_MODULE) => module -> ^(CLTEXT module)
>
>          | text -> ^(CLTEXT text)
>
>          ;
>
>
>
> module
>
>          : OPEN CL_MODULE interpretablename exclusion_set? cltext CLOSE ->
> ^(MODULE ^(MODULE_IDENTIFIER interpretablename) exclusion_set? cltext)
>
>          ;
>
>
>
> text
>
>          : phrase* -> ^(TEXT phrase*)
>
>          ;
>
> ...
>
>
>
>
>
>
>
> On Thu, Apr 8, 2010 at 3:57 PM, Jim Idle <jimi at temporal-wave.com> wrote:
>
> You probably need to send the grammar rather than that graphic. It is
> likely something more fundamental and we cannot see what you predicates are
> doing from the graphic.
>
> Jim
>
>
> > -----Original Message-----
> > From: antlr-interest-bounces at antlr.org [mailto:antlr-interest-
> > bounces at antlr.org] On Behalf Of Cameron Ross
> > Sent: Thursday, April 08, 2010 12:34 PM
> > To: antlr-interest at antlr.org
> > Subject: [antlr-interest] OPEN, EOF ambiguity
> >
> > Hi,
> >
> > I have a grammar with an ambiguity that I just can't resolve.  When I
> > check the grammar using AntlrWorks I get the following: "Decision can
> > match input such as "{EOF, OPEN}" using multiple alternatives: 1, 2".
> > I've attached a screen grab of the syntax diagram generated by
> > AntrlWorks.  I don't understand why ANLTR is thinking that EOF is
> > ambiguous with OPEN.  I've checked the grammar and clif_file is the
> > only rule that is not referenced from within the grammar, so I don't
> > think that ANLTR should see module as a start rule.  Any help is much
> > appreciated.
> >
> > Cameron
>
>
>
>
>
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>
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>
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