-- pattern matching
module test035;

import Stdlib.Prelude open;

lgen : Nat → List Nat
  | zero := nil
  | (suc n) := suc n :: lgen n;

sum2 : List Nat → List Nat
  | (x :: y :: xs) := x + y :: sum2 (y :: xs)
  | xs := xs;

type Tree :=
  | leaf : Tree
  | node : Tree -> Tree -> Tree;

gen : Nat → Tree
  | zero := leaf
  | (suc zero) := node leaf leaf
  | (suc (suc n)) := node (gen n) (gen (suc n));

terminating
f : Tree → Nat
  | leaf := 1
  | (node l r) :=
    case g l, g r
      | leaf, leaf := 3
      | node l r, leaf := mod ((f l + f r) * 2) 20000
      | node l1 r1, node l2 r2 :=
        mod ((f l1 + f r1) * (f l2 + f r2)) 20000
      | _, node l r := mod (f l + f r) 20000;

g : Tree → Tree
  | leaf := leaf
  | (node (node _ _) r) := r
  | (node l r) := node r l;

h : Nat -> Nat
  | (suc (suc (suc (suc n)))) := n
  | _ := 0;

printListNatLn : List Nat → IO
  | nil := printStringLn "nil"
  | (x :: xs) :=
    printNat x >> printString " :: " >> printListNatLn xs;

main : IO :=
  printListNatLn (sum2 (lgen 5))
    >> printNatLn (f (gen 10))
    >> printNatLn (f (gen 15))
    >> printNatLn (f (gen 16))
    >> printNatLn (f (gen 17))
    >> printNatLn (f (gen 18))
    >> printNatLn (f (gen 20))
    >> printNatLn (h 5)
    >> printNatLn (h 3);