src/pexprs.js
function Extend(superGrammar, name, body) {
  this.superGrammar = superGrammar;
  this.name = name;
  this.body = body;
  var origBody = superGrammar.rules[name].body;
  this.terms = [body, origBody];
}
function Extend(superGrammar, name, body) {
  this.superGrammar = superGrammar;
  this.name = name;
  this.body = body;
  var origBody = superGrammar.rules[name].body;
  this.terms = [body, origBody];
}
function Extend ( superGrammar , name , body ) { this . superGrammar = superGrammar ; this . name = name ; this . body = body ; var origBody = superGrammar . rules [ name ] . body ; this . terms = [ body , origBody ] ; }
Extend is an implementation detail of rule extension
Extend is an implementation detail of rule extension