Created
November 7, 2012 20:41
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Type Level Associative Array
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{-# LANGUAGE PolyKinds, DataKinds, TemplateHaskell, TypeFamilies, | |
GADTs, TypeOperators, RankNTypes, FlexibleContexts, UndecidableInstances, | |
FlexibleInstances, ScopedTypeVariables, MultiParamTypeClasses, | |
OverlappingInstances, TemplateHaskell #-} | |
module Oxymoron.Regions.TAssociativeArray where | |
import Data.Singletons | |
singletons [d| data AssocArray a b = AssocArray [(a, b)] |] | |
type instance ('AssocArray xs) :==: ('AssocArray ys) = | |
If ((xs :==: '[ ]) :&&: (ys :==: '[ ])) | |
True | |
(If (xs :==: '[ ]) False ( | |
If (ys :==: '[ ]) | |
False | |
(xs :==: (Reorder ys xs)) | |
)) | |
type instance '(a, b) :==: '(x, y) = (a :==: x) :&&: (b :==: y) | |
type family Fst (x :: (a,b)) :: a | |
type instance Fst '(a,b) = a | |
type family Snd (x :: (a,b)) :: b | |
type instance Snd '(a,b) = b | |
-- remove a DimSpec from a list, if it's in the list; | |
-- returns the new list and possibly the extracted element | |
type family Extract (s :: k) (lst :: [k]) :: ([k], Maybe k) | |
type instance Extract s '[] = '( '[], Nothing) | |
type instance Extract s (h ': t) = | |
If (s :==: h) | |
'(t, Just h) | |
'(h ': Fst (Extract s t), Snd (Extract s t)) | |
-- reorder 'a' in the order defined by 'b'. | |
type family Reorder (a :: [k]) (b :: [k]) :: [k] | |
type instance Reorder x '[] = x | |
type instance Reorder x (h ': t) = Reorder' (Extract h x) t | |
type family Reorder' (scrut :: ([k], Maybe k)) | |
(t :: [k]) | |
:: [k] | |
type instance Reorder' '(lst, Nothing) t = Reorder lst t | |
type instance Reorder' '(lst, Just elt) t = elt ': (Reorder lst t) | |
singletons [d| data TestValue = Test1 | |
| Test2 | |
| Test3 | |
deriving(Eq, Show) | |
data TestKey = Key1 | |
| Key2 | |
| Key3 | |
deriving(Eq, Show) | |
|] | |
test :: ((a :==: b) ~ True) => Sing (a :: AssocArray k v) -> Sing (b :: AssocArray k v) -> Int | |
test = undefined | |
testA :: Sing ('AssocArray '[ '( 'Key1, 'Test3 ), | |
'( 'Key2, 'Test2 )]) | |
testA = undefined | |
testB :: Sing ('AssocArray '[ '( 'Key2, 'Test2), | |
'( 'Key1, 'Test3)]) | |
testB = undefined | |
testC :: Sing ('AssocArray '[ '( 'Key2, 'Test3) ]) | |
testC = undefined | |
-- Order is different but it still compiles | |
test1 = test testA testB | |
-- this won't compile | |
--test2 = test testA testC |
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