anchor.diff: -%% Copyright (c) 2014 Robert Virding
  +%% Copyright (c) 2014-2018 Robert Virding
   %%
   %% Licensed under the Apache License, Version 2.0 (the "License");
   %% you may not use this file except in compliance with the License.
  
positive.code: new(Name) ->
      ets:new(Name, [named_table,set,protected,{keypos,1}]).
  
  %% add_built_in(Functor, Database) -> NewDatabase.
  %%  Add Functor as a built-in in the database.
  
  add_built_in(Db, Functor) ->
  
negative.code: 	[] -> undefined				%Undefined
      end.
  
  %% get_interp_functors(Db) -> [Functor].
  
  get_interpreted_functors(Db) ->
      ets:foldl(fun ({Func,clauses,_,_}, Fs) -> [Func|Fs];
  