code: private ExprKraken parseAddExpr()
    {
      ExprKraken left = parseMulExpr();
  
      while (true) {
        Token token = scanToken();
  
        switch (token) {
        case PLUS:
          left = new BinaryExpr(BinaryOp.ADD, left, parseSimpleTerm());
          break;
        case MINUS:
          left = new BinaryExpr(BinaryOp.SUB, left, parseSimpleTerm());
          break;
  
        default:
          _token = token;
          return left;
        }
      }
    }
docs: Parses a +/- expression.