anchor.diff:  %% -----------------------------------------------------------------------------
   %% Operations:
   %%
  -%% - empty(O): returns empty B-tree of order O. Order is defined as 
  +%% - empty(O): returns empty B-tree of order O. Order is defined as
   %%   the maximum number of children nodes a non-leaf node may hold.
   %%   The minimum value is 4.
   %%
  -%% - empty(O, b_star): returns empty B*-tree of order O. Order is 
  -%%   defined as the maximum number of children nodes a non-leaf node 
  +%% - empty(O, b_star): returns empty B*-tree of order O. Order is
  +%%   defined as the maximum number of children nodes a non-leaf node
   %%   may hold. The minimum value is 4.
   %%
  -%% - enter(K, V, B): inserts key K with value V into B-tree / B*-tree B 
  -%%   if the key is not present in the tree, otherwise updates key K to 
  +%% - enter(K, V, B): inserts key K with value V into B-tree / B*-tree B
  +%%   if the key is not present in the tree, otherwise updates key K to
   %%   value V in B. Returns the new tree.
   %%
   %% - from_dict(O, L): turns a list L of {Key, Value} pairs into
  
positive.code: 
  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  %% Data structure:
  %% - {BTreeType, Minimum, Maximum, NumberKeyValues, Tree}, 
  %%   where `Tree' is composed of :
  %%   - {KeyNo, IsLeaf, [{Key, Value}], [Tree]}.
  
  
negative.code: %% - from_dict(O, b_star, L): turns a list L of {Key, Value} pairs into
  %%   a B*-tree of order O. The list must not contain duplicate keys.
  %%
  %% - get(K, B): retrieves the value stored with key K in
  %%   B-tree / B*-tree T. Assumes that the key is present in the tree.
  %%
  %% - height(B): returns the height of the B-tree / B*-tree B as an integer.
  %%   Returns 0 (zero) if the B-tree / B*-tree B is empty.
  %%
  %% - insert(K, V, B): inserts key K with value V into B-tree / B*-tree B;
  %%   returns the new B-tree / B*-tree. Assumes that the key K is *not*
  %%   present in the B-tree / B*-tree B.
  %%
  %% - is_defined(K, B): returns `true' if key K is present in
  %%   B-tree / B*-tree B, and `false' otherwise.
  %%
  %% - is_empty(B): returns 'true' if B is an empty B-tree / B*-tree,
  %%   and 'false' otherwise.
  %%
  %% - iterator(B): returns an iterator that can be used for traversing
  %%   the entries of B-tree / B*-tree B; see `next'. The implementation
  %%   of this is very efficient; traversing the whole tree using `next'
  %%   is only slightly slower than getting the list of all elements using
  %%   `to_list' and traversing that. The main advantage of the iterator
  