#!/usr/bin/perl -w

use vars qw( %base %man @try_again );
use Parse::RecDescent;
sub Parse::RecDescent::choose { $_[1 + int rand $#_]; }

$abbott = new Parse::RecDescent <<'EOABBOTT';
        Interpretation: ConfirmationRequest | NameRequest | BaseRequest
        ConfirmationRequest:
                Preface(s?) Name /[i']s on/ Base
                        { (lc $::man{$item[4]} eq lc $item[2]) ? "Yes"
                                "No, $::man{$item[4]}\'s on $item[4]" }
                | Preface(s?) Name /[i']s the (name of the)?/
                Man /('s name )?on/ Base
                        { (lc $::man{$item[6]} eq lc $item[2]) ? "Certainly"
                                : "No. \u$item[2] is on " . $::base{lc $item[2]} }
        BaseRequest:
                Preface(s?) Name /(is)?/
                        { "He's on " . $::base{lc $item[2]} }
        NameRequest:
                /(What's the name of )?the/i Base "baseman"
                        { $::man{$item[2]} }
        Preface: ...!Name /\S*/
        Name: Name12 | /I Don't Know/i
        Name12: /Who/i | /What/i
        Base: 'first' | 'second' | 'third'
        Man: 'man' | 'guy' | 'fellow'
EOABBOTT

$costello = new Parse::RecDescent <<'EOCOSTELLO';
        Interpretation:
                Meaning <reject:$item[1] eq $thisparser->{prev}>
                                { $thisparser->{prev} = $item[1] }
                        | { choose(@::try_again) }
         Meaning: Question | UnclearReferent | NonSequitur
         Question:
                 Preface Interrogative /[i']s on/ Base
                        { choose ("Yes, what is the name of the guy on $item[4]?",
                                  "The $item[4] baseman?", "I'm asking you! $item[2]?",
                                  "I don't know!") }
                | Interrogative
                         { choose ("That's right, $item[1]?", "What?","I don't know!") }
          UnclearReferent: "He's on" Base
                              { choose ("Who's on $item[2]?", "Who is?",
                                        "So, what is the name of the guy on $item[2]?" ) }
          NonSequitur: ( "Yes" | 'Certainly' | /that's correct/i )
                              { choose("$item[1], who?", "What?", @::try_again) }
          Interrogative: /who/i | /what/i
          Base: 'first' | 'second' | 'third'
          Preface: ...!Interrogative /\S*/
EOCOSTELLO

%man = ( first => "Who", second => "What", third => "I Don't Know" );
%base = map { lc } reverse %man;

@try_again = ( "So, who's on first?", "I want to know who's on first!",
               "What's the name of the first baseman?",
               "Let's start again. What's the name of the guy on first?",
               "Okay, then, who's on second?", "Well then, who's on third?",
               "What's the name of the fellow on third?" );
				
$costello->{prev} = $line = "Who's on first?";

while (1) {
        print " ", $line, "\n" and sleep 1;
        $line = $abbott->Interpretation($line);
        print " ", $line, "\n" and sleep 1;
        $line = $costello->Interpretation($line);
}