anchor.diff:  
   %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
   %% Data structure:
  -%% - {BTreeType, Minimum, Maximum, NumberKeyValues, Tree}, 
  +%% - {BTreeType, Minimum, Maximum, NumberKeyValues, Tree},
   %%   where `Tree' is composed of :
   %%   - {KeyNo, IsLeaf, [{Key, Value}], [Tree]}.
   
  
positive.code: %%   traversing the remaining entries, or the atom `none' if no entries
  %%   remain.
  %%
  %% - number_key_values(B): returns the number of key / value pairs in the 
  %%   B-tree / B*-tree B as an integer. Returns 0 (zero) if the 
  %%   B-tree / B*-tree B is empty.
  %%
  %% - size(B): returns the number of nodes in the B-tree / B*-tree B 
  %%   as an integer. Returns 0 (zero) if the B-tree / B*-tree B is empty.
  %%
  %% - smallest(B): returns {K, V}, where K is the smallest key in 
  %%   B-tree / B*-tree B, and V is the value associated with K in B. 
  %%   Assumes that the B-tree / B*-tree B is nonempty.
  %%
  %% - to_list(B): returns an ordered list of {Key, Value} pairs 
  %%   for all keys in B-tree / B*-tree B.
  
  %% - update(K, V, B): updates key K to value V in B-tree / B*-tree B; 
  %%   returns the new tree. Assumes that the key is present in the tree.
  %%
  %% - values(B): returns the list of values for all keys in 
  %%   B-tree / B*-tree B, sorted by their corresponding keys. 
  %%   Duplicates are not removed.
  %%
  
  
negative.code: %% -----------------------------------------------------------------------------
  %% Operations:
  %%
  %% - 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
  %%   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
  %%   value V in B. Returns the new tree.
  %%
  %% - from_dict(O, L): turns a list L of {Key, Value} pairs into
  