message: Support parentheses in arithmetic expressions.
diff: @@ -331,6 +331,9 @@ parse_term(Src, Expr, !PS) :-
  Expr = expr_const(N)
  else if int_literal(Src, N, !PS) then
  Expr = expr_const(N)
  + else if punct("(", Src, _, !PS) then
  + parse_expr_int(Src, Expr, !PS),
  + punct(")", Src, _, !PS)
  else
  identifier(Src, Ident, !PS),
  ( if
  