/tutorial/backtracking/tiny_prolog/prolog_commons.e

 1class PROLOG_COMMONS
 2feature
 3	type_atom, type_integer, type_float, type_compound, type_var: INTEGER is unique
 4	builtins: AVL_DICTIONARY[ROUTINE[ANY,TUPLE[]],PROLOG_FUNCTOR] is
 5		once
 6			create Result
 7		end
 8	atoms: HASHED_DICTIONARY[PROLOG_ATOM,STRING] is
 9		once
10			create Result
11		end
12	get_functor_by_name(name: STRING; arity: INTEGER): PROLOG_FUNCTOR is
13		do
14			Result := get_functor_by_atom(get_atom_by_name(name),arity)
15		end
16	get_functor_by_atom(atom: PROLOG_ATOM; arity: INTEGER): PROLOG_FUNCTOR is
17		do
18			create Result.make(atom,arity)
19		end
20	get_atom_by_name(name: STRING): PROLOG_FUNCTOR is
21		do
22			Result := atoms.reference_at(name)
23			if Result = Void then
24				create Result.make(name.twin)
25				atoms.add(Result,Result.name)
26			end
27		end
28end
29