7260c24 · generic-lens

git.iko.soy/generic-lens

Improve inference for param

commit7260c2498fed872cc43449ad04354155c4535de4 authorCsongor Kiss <kiss.csongor.kiss@gmail.com> dateFri 9 Mar 2018, 16:32 (9 years ago) parent3e9221c

2 files changed+10−2

compare with master

unifiedsplit

src/Data/Generics/Internal/Families/Changing.hs+6 src/Data/Generics/Product/Param.hs+4−2

src/Data/Generics/Internal/Families/Changing.hs+6

@@ -14,6 +14,7 @@ module Data.Generics.Internal.Families.Changing

1414 , PTag (..)

1515 , P

1616 , LookupParam

17+ , ArgAt

1718 , ArgCount

1819 ) where

1920

@@ -123,6 +124,11 @@ type family ArgCount (t :: k) :: Nat where

123124 ArgCount (f a) = 1 + ArgCount f

124125 ArgCount a = 0

125126

127+type family ArgAt (t :: k) (n :: Nat) :: j where

128+ ArgAt (t a) 0 = a

129+ ArgAt (t a) n = ArgAt t (n - 1)

130+

131+

126132-- Note [CPP in instance constraints]

127133-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

128134--

src/Data/Generics/Product/Param.hs+4−2

@@ -1,3 +1,4 @@

1+{-# LANGUAGE PolyKinds #-}

12{-# LANGUAGE TypeFamilies #-}

23{-# LANGUAGE AllowAmbiguousTypes #-}

34{-# LANGUAGE DataKinds #-}

@@ -33,14 +34,13 @@ import GHC.TypeLits

3334import Data.Generics.Internal.Void

3435import Data.Generics.Internal.Families.Changing

3536import Data.Generics.Internal.VL.Traversal

36−import Data.Generics.Internal.VL.Lens

3737

3838import GHC.Generics

3939import Data.Kind

4040import Data.Generics.Internal.VL.Iso

4141import Data.Generics.Internal.GenericN

4242

43−class HasParam (p :: Nat) s t a b | p t a b -> s, p s a b -> t where

43+class HasParam (p :: Nat) s t a b | p t a b -> s, p s a b -> t, p s -> a, p t -> b where

4444 param :: Applicative g => (a -> g b) -> s -> g t

4545

4646instance

@@ -50,6 +50,8 @@ instance

5050 , s ~ Infer t (P n b 'PTag) a

5151 , t ~ Infer s (P n a 'PTag) b

5252 , Error ((ArgCount s) <=? n) n (ArgCount s) s

53+ , a ~ ArgAt s n

54+ , b ~ ArgAt t n

5355 , GHasParam n (RepN s) (RepN t) a b

5456 ) => HasParam n s t a b where

5557