Data commit

Task/Church-numerals/Erlang/church-numerals.erl

@@ -0,0 +1,20 @@
+-module(church).
+-export([main/1, zero/1]).
+zero(_)    -> fun(F) -> F end.
+succ(N)    -> fun(F) -> fun(X) -> F((N(F))(X)) end end.
+add(N,M)   -> fun(F) -> fun(X) -> (M(F))((N(F))(X)) end end.
+mult(N,M)  -> fun(F) -> fun(X) -> (M(N(F)))(X) end end.
+power(B,E) -> E(B).
+
+to_int(C) -> CountUp = fun(I) -> I + 1 end, (C(CountUp))(0).
+
+from_int(0) -> fun church:zero/1;
+from_int(I) -> succ(from_int(I-1)).
+
+main(_) ->
+    Zero  = fun church:zero/1,
+    Three = succ(succ(succ(Zero))),
+    Four  = from_int(4),
+    lists:map(fun(C) -> io:fwrite("~w~n",[to_int(C)]) end,
+	      [add(Three,Four),   mult(Three,Four),
+	       power(Three,Four), power(Four,Three)]).