message: Update calculator_pure_grammar.js
diff: @@ -167,8 +167,10 @@ CalculatorPure.prototype.constructor = CalculatorPure
  var parser = new CalculatorPure([])
  // ----------------- Interpreter -----------------
  +// Obtains the default CstVisitor constructor to extend.
  const BaseCstVisitor = parser.getBaseCstVisitorConstructor()
  +// All our semantics go into the visitor, completly separated from the grammar.
  class CalculatorInterpreter extends BaseCstVisitor {
  constructor() {
  super()
  