[antlr-interest] Enforcing a right associativity, to resolve an ambiguity (simple grammar included)

[Naveen Chawla]

Hi,

I'm a little bit stumped. You might find this easy. I'm trying to develop an
English parser and have come across a real ambiguity in English, on
which, for the time being, I just want to enforce simple right
associativity:

e.g. Recommending drinking while driving is dangerous.

(Is it referring to the person driving while they are recommending drinking,
or the person recommending drinking-during-driving?)

This is not a problem. Since they are both equally valid in English, for the
time being I just want to enforce right associativity (maybe later give a
user option to change the tree), but I cannot figure out how!! Here is the
grammar I want to make right-associative (simplified for your convenience):

grammar prep;
sentence: nounPhrase 'verb';

            nounPhrase: 'Ving' complement? prepPhr?;

                           complement : nounPhrase 'noun'? ;

                           prepPhr: 'preposition' nounPhrase;


Ambiguous sentence example: "Ving Ving preposition Ving verb"
Ambiguity: "preposition" can be a prepPhr belonging to the first "Ving"
(nounPhrase) OR the second "Ving" (nounPhrase). I want prepPhr to always
belong to the last occurring 'Ving' (nounPhrase). So I want to
enforce, using the example sentence (right associativity):

 sentence{
         nounPhrase{
                   'Ving'
                    complement{
                                nounPhrase{
                                             'Ving'
                                              prepPhr{
                                                           'preposition'
                                                           nounPhrase{
                                                                          'Ving'
                                                            }
                                              }
                                }
                   }
         }
         'verb'
}

instead of

 sentence{
         nounPhrase{
                   'Ving'
                    complement{
                                nounPhrase{
                                             'Ving'
                                }
                     }
                     prepPhr{
                                'preposition'
                                nounPhrase{
                                             'Ving'
                                 }
                      }
         }
         'verb'
}

while preserving the grammar.
Anybody have as easy idea how? Sorry if I sound newbie, I'm stumped.

Regards,
N
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