module TestCase

-- I'm testing cases here, but using examples carefully design to be
-- simple case trees. Patterns are a var or a constructor applied to vars.

-- There are indexes below, but we're got pulling constraints out of them yet.



data Nat : U where
  Z : Nat
  S : Nat -> Nat

data Vect : Nat -> U -> U where
  Nil : {a : U} -> Vect Z a
  Cons : {a : U} {n : Nat} -> a -> Vect n a -> Vect (S n) a

plus : Nat -> Nat -> Nat
plus = \ n m => case n of
  Z => m
  S k => S (plus k m)

-- Example from Jesper talk (translated to explicit case tree)
max : Nat -> Nat -> Nat
max = \ n m => case n of
  Z => m
  S k => case m of
    Z => S k
    S l => S (max k l)

length : {a : U} {n : Nat} -> Vect n a -> Nat
length = \ v => case v of
  Nil => Z
  Cons x xs => S (length xs)

data Unit : U where
  MkUnit : Unit

-- This should fail (and does!)
-- bar : Vect (S Z) Unit
-- bar = (Cons MkUnit (Cons MkUnit Nil))

data Bool : U where
  True : Bool
  False : Bool

not : Bool -> Bool
not = \ v => case v of
  True => False
  False => True


not2 : Bool -> Bool
not2 = \ v => case v of
  True => False
  x => True

and : Bool -> Bool -> Bool
and = \ x y => case x of
  True => y
  False => False

-- FIXME - a case is evaluated here, and I don't know why.

nand : Bool -> Bool -> Bool
nand = \ x y => not (case x of
    True => y
    False => False)

-- -- this should be an error.
-- foo : Bool -> Bool

data Void : U where

foo : Int
foo = 42