Data commit

Task/Ackermann-function/Coq/ackermann-function-1.coq

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+Fixpoint ack (m : nat) : nat -> nat :=
+  fix ack_m (n : nat) : nat :=
+    match m with
+      | 0 => S n
+      | S pm =>
+        match n with
+          | 0 => ack pm 1
+          | S pn => ack pm (ack_m pn)
+        end
+    end.
+
+
+(*
+  Example:
+    A(3, 2) = 29
+*)
+
+Eval compute in ack 3 2.

Task/Ackermann-function/Coq/ackermann-function-2.coq

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+Require Import Utf8.
+
+Section FOLD.
+  Context {A : Type} (f : A → A) (a : A).
+  Fixpoint fold (n : nat) : A :=
+    match n with
+      | O => a
+      | S k => f (fold k)
+    end.
+End FOLD.
+
+Definition ackermann : nat → nat → nat :=
+  fold (λ g, fold g (g (S O))) S.