anchor.diff:  interval_sort(all, _Interval2) ->
       true;
   interval_sort({element, A}, {element, B}) ->
  -    greater_equals_than(B, A);
  +    B >= A;
   interval_sort({element, A}, {interval, _B0Br, B0, _B1, _B1Br}) ->
  -    greater_equals_than(B0, A);
  +    B0 >= A;
   interval_sort({interval, _A0Br, A0, _A1, _A1Br}, {element, B}) ->
  -    greater_than(B, A0);
  +    B > A0;
   interval_sort({interval, A0Br, A0, _A1, _A1Br} = A, {interval, B0Br, B0, _B1, _B1Br} = B) ->
       % beware of not accidentally making two intervals equal, which is defined
       % as A==B <=> interval_sort(A, B) andalso interval_sort(B, A)
  -    greater_than(B0, A0) orelse
  +    B0 > A0 orelse
           (A0 =:= B0 andalso A0Br =:= '[' andalso B0Br =:= '(') orelse
           (A0 =:= B0 andalso (not (A0Br =:= '(' andalso B0Br =:= '[')) andalso A =< B);
   interval_sort(_Interval1, _Interval2) ->
  
positive.code: % @doc Begin &lt;= X &lt;= End
  % precondition Begin &lt;= End
  -spec is_between(BeginBr::left_bracket(), Begin::key(), X::key(), End::key(), EndBr::right_bracket()) -> boolean().
  is_between('[', Begin, X, End, ']') ->
      greater_equals_than(X, Begin) andalso greater_equals_than(End, X);
  is_between('[', Begin, X, End, ')') ->
      greater_equals_than(X, Begin) andalso greater_than(End, X);
  is_between('(', Begin, X, End, ']') ->
      greater_than(X, Begin) andalso greater_equals_than(End, X);
  is_between('(', Begin, X, End, ')') ->
      greater_than(X, Begin) andalso greater_than(End, X).
  
  %% @doc A &gt; B
  -spec greater_than(A::key(), B::key()) -> boolean().
  greater_than(X, Y) -> X > Y.
  
  %% @doc A &gt;= B
  -spec greater_equals_than(A::key(), B::key()) -> boolean().
  greater_equals_than(A, B) -> (A =:= B) orelse greater_than(A, B).
  
  %% @doc X and Y are adjacent and Y follows X
  -spec is_left_of(interval(), interval()) -> boolean().
  
negative.code: is_well_formed_simple({interval, _LeftBr, _X, ?PLUS_INFINITY, ')'}) ->
      true;
  is_well_formed_simple({interval, _LeftBr, X, Y, _RightBr}) ->
      X < Y;
  is_well_formed_simple(all) -> true;
  is_well_formed_simple(_) -> false.
  
  