#! /usr/local/bin/perl -sw
# extend-grammar.pl by Teodor Zlatanov, tzz@iglou.com
# March 26, 2000

# A script that extends the proper names it knows, as they are added
# with the "name exists" command.

# based on demo_selfmod.pl: A SELF-MODIFYING**2 PARSER
# from the Parse::RecDescent distribution

use Parse::RecDescent;

$grammar =
q{
  process: query | definition

  query: do_you_know proper_name { print "I know " . $item{proper_name} . ", sure!\n" }
  query: do_you_know name { print $item{name} . " does not exist in my little world, sorry.\n" }

  definition: name /exists/i
		       { $thisparser->Extend("proper_name: '$item{name}'");
			  print "\"$item{name}\" is now a valid proper name\n";
		       }
  proper_name: /Ted/
  name: /\w+/
  do_you_know: /do/i /you/i /know/i
};

$parse = new Parse::RecDescent ($grammar);

while (<>)
{
 $parse->process($_) or print "Enter a query (do you know ...) or a definition (... exists)\n";
}