Sync

Task/Gray-code/Prolog/gray-code-2.pro

@@ -0,0 +1,31 @@
+:- use_module(library(apply)).
+
+to_gray(N, G) :-
+  N0 is N >> 1,
+  G is N xor N0.
+
+from_gray(G, N) :-
+  ( G > 0
+  ->  S is G >> 1,
+      from_gray(S, N0),
+      N is G xor N0
+  ;   N is G ).
+
+make_num(In, Out) :-
+  atom_to_term(In, Out, _),
+  integer(Out).
+
+write_record(Number, Gray, Decoded) :-
+  format('~w~10|~2r~10+~2r~10+~2r~10+~w~n',
+         [Number, Number, Gray, Decoded, Decoded]).
+
+go :-
+  setof(N, between(0, 31, N), Numbers),
+  maplist(to_gray, Numbers, Grays),
+  maplist(from_gray, Grays, Decodeds),
+  format('~w~10|~w~10+~w~10+~w~10+~w~n',
+         ['Number', 'Binary', 'Gray', 'Decoded', 'Number']),
+  format('~w~10|~w~10+~w~10+~w~10+~w~n',
+         ['------', '------', '----', '-------', '------']),
+  maplist(write_record, Numbers, Grays, Decodeds).
+go :- halt(1).