Prolog in OMeta/JS

This page "autoexecs" the example from the OMeta/JS demo page that adds support for method declarations to the SqueakParser and a tiny Prolog engine (less than 100 lines of JavaScript), then implements Prolog syntax using OMeta/JS. To make it go, select all of the code below and press the "do it" button. When a solution pops up, press OK to accept it, or Cancel to search for the next one.

ometa PrologTranslator : Parser {
  variable     ::= <spaces> <firstAndRest #upper #letterOrDigit>:name           => [Var new: (name join: '')].
  symbol       ::= <spaces> <firstAndRest #lower #letterOrDigit>:name           => [Sym new: (name join: '')].
  clause       ::= <symbol>:sym <token '('> <listOf #expr ','>:args <token ')'> => [Clause new: sym : args].
  expr         ::= <clause> | <variable> | <symbol>.
  clauses      ::= <listOf #clause ','>.
  rule         ::= <clause>:head <token ':-'> <clauses>:body <token '.'>        => [Rule new: head : body]
                 | <clause>:head                             <token '.'>        => [Rule new: head : {}].
  rules        ::= <rule>*:rs <spaces> <end>                                    => [rs].
  query        ::= <clause>:c <spaces> <end>                                    => [c].
}.

PrologTranslator answer: query withRules: rules [
  solve
    value: (PrologTranslator matchAll: query with: #query)
    value: (PrologTranslator matchAll: rules with: #rules).
].

PrologTranslator answer: 'grandfather(X, Y)' withRules: '
  father(abe, homer).
  father(homer, lisa).
  father(homer, bart).
  grandfather(X, Y) :- father(X, Z), father(Z, Y).
'.

Acknowledgement: the tiny Prolog engine used in this page was joint work with Stephen Murrell.