lib/ProductionRule.js
function ProductionRule(lhs, rhs, head) {
  this.lhs = lhs;
  this.rhs = rhs;
  this.head = head;
  // feature structure of the constraints specified with the rule
  this.fs = null;
}
function ProductionRule(lhs, rhs, head) {
  this.lhs = lhs;
  this.rhs = rhs;
  this.head = head;
  // feature structure of the constraints specified with the rule
  this.fs = null;
}
function ProductionRule ( lhs , rhs , head ) { this . lhs = lhs ; this . rhs = rhs ; this . head = head ; // feature structure of the constraints specified with the rule this . fs = null ; }
Constructor - lhs is a string - rhs is an array of strings - head is a number pointing to a rhs nonterminal
Constructor - lhs is a string - rhs is an array of strings - head is a number pointing to a rhs nonterminal