1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
|
{-# LANGUAGE GADTs, TypeFamilies, DataKinds, PolyKinds, TypeOperators #-}
{-# LANGUAGE TemplateHaskell #-}
{-# OPTIONS_GHC -O -fplugin-opt=Test.Inspection.Plugin:quiet -Wno-overlapping-patterns #-}
module NS_NP (main) where
import Data.Kind
import Test.Inspection
data NS (f :: k -> Type) (xs :: [k]) where
Z :: f x -> NS f (x : xs)
S :: !(NS f xs) -> NS f (x : xs)
data NP (f :: k -> Type) (xs :: [k]) where
Nil :: NP f '[]
(:*) :: f x -> !(NP f xs) -> NP f (x : xs)
newtype I a = I a
from :: Ordering -> NS (NP I) '[ '[], '[], '[] ]
from = \ x -> case x of
LT -> Z Nil
EQ -> S (Z Nil)
GT -> S (S (Z Nil))
{-# INLINE from #-}
to :: NS (NP I) '[ '[], '[], '[] ] -> Ordering
to = \ x -> case x of
(Z Nil) -> LT
(S (Z Nil)) -> EQ
(S (S (Z Nil))) -> GT
_ -> error "unreachable"
{-# INLINE to #-}
roundtrip :: Ordering -> Ordering
roundtrip = to . from
{-# INLINE roundtrip #-}
roundtrip_id :: Ordering -> Ordering
roundtrip_id x = x
main :: IO ()
main = return ()
inspect $ 'roundtrip === 'roundtrip_id
|
