A-M baby

Task/Factorial/Prolog/factorial-1.pro

@@ -0,0 +1,2 @@
+fact(X, 1) :- X<2.
+fact(X, F) :- Y is X-1, fact(Y,Z), F is Z*X.

Task/Factorial/Prolog/factorial-2.pro

@@ -0,0 +1,8 @@
+fact(N, NF) :-
+	fact(1, N, 1, NF).
+
+fact(X, X, F, F) :- !.
+fact(X, N, FX, F) :-
+	FX1 is FX * X,
+	X1 is X + 1,
+	fact(X1, N, FX1, F).

Task/Factorial/Prolog/factorial-3.pro

@@ -0,0 +1,13 @@
+% foldl(Pred, Init, List, R).
+%
+foldl(_Pred, Val, [], Val).
+foldl(Pred, Val, [H | T], Res) :-
+	call(Pred, Val, H, Val1),
+	foldl(Pred, Val1, T, Res).
+
+% factorial
+p(X, Y, Z) :- Z is X * Y).
+
+fact(X, F) :-
+	numlist(2, X, L),
+	foldl(p, 1, L, F).

Task/Factorial/Prolog/factorial-4.pro

@@ -0,0 +1,12 @@
+:- use_module(lambda).
+
+% foldl(Pred, Init, List, R).
+%
+foldl(_Pred, Val, [], Val).
+foldl(Pred, Val, [H | T], Res) :-
+	call(Pred, Val, H, Val1),
+	foldl(Pred, Val1, T, Res).
+
+fact(N, F) :-
+	numlist(2, N, L),
+	foldl(\X^Y^Z^(Z is X * Y), 1, L, F).

Task/Factorial/Prolog/factorial-5.pro

@@ -0,0 +1,14 @@
+:- use_module(lambda).
+
+fact(N, FN) :-
+	cont_fact(N, FN, \X^Y^(Y = X)).
+
+cont_fact(N, F, Pred) :-
+	(   N = 0 ->
+	    call(Pred, 1, F)
+	;   N1 is N - 1,
+
+	    P =  \Z^T^(T is Z * N),
+	    cont_fact(N1, FT, P),
+	    call(Pred, FT, F)
+	).