code: public static Expression parse(Reader input, Scope scope) throws ParseException {
          return new Parser(input, scope).parse();
      }
docs: Parses the given input into an expression.
  <p>
  Referenced variables will be resolved using the given Scope
  
  @param input the expression to be parsed
  @param scope the scope used to resolve variables
  @return the resulting AST as expression
  @throws ParseException if the expression contains one or more errors