Just another update

Task/Factorial/Mercury/factorial-1.mercury

@@ -0,0 +1,16 @@
+:- module factorial.
+
+:- interface.
+:- import_module integer.
+
+:- func factorial(integer) = integer.
+
+:- implementation.
+
+:- pragma memo(factorial/1).
+
+factorial(N) =
+    (   N =< integer(0)
+    ->  integer(1)
+    ;   factorial(N - integer(1)) * N
+    ).

Task/Factorial/Mercury/factorial-2.mercury

@@ -0,0 +1,18 @@
+:- module test_factorial.
+:- interface.
+:- import_module io.
+
+:- pred main(io::di, io::uo) is det.
+
+:- implementation.
+:- import_module factorial.
+:- import_module char, integer, list, string.
+
+main(!IO) :-
+    command_line_arguments(Args, !IO),
+    filter(is_all_digits, Args, CleanArgs),
+    Arg1 = list.det_index0(CleanArgs, 0),
+    Number = integer.det_from_string(Arg1),
+    Result = factorial(Number),
+    Fmt = integer.to_string,
+    io.format("factorial(%s) = %s\n", [s(Fmt(Number)), s(Fmt(Result))], !IO).

Task/Factorial/Mercury/factorial-3.mercury

@@ -0,0 +1 @@
+factorial(100) = 93326215443944152681699238856266700490715968264381621468592963895217599993229915608941463976156518286253697920827223758251185210916864000000000000000000000000