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Try a different approach

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Taylor Fausak 2020-11-18 13:56:38 -05:00
parent 705fd76001
commit 20cde91d56
1 changed files with 6 additions and 6 deletions
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12
src/lib/Witch.hs
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@ -1,4 +1,6 @@
{-# language AllowAmbiguousTypes #-}
{-# language ConstraintKinds #-}
{-# language DataKinds #-}
{-# language DefaultSignatures #-}
{-# language FlexibleInstances #-}
{-# language MultiParamTypeClasses #-}
@ -50,6 +52,7 @@ import qualified Data.Set as Set
import qualified Data.Text as Text
import qualified Data.Text.Lazy as LazyText
import qualified Data.Tuple as Tuple
import qualified Data.Type.Equality as Type
import qualified Data.Void as Void
import qualified Data.Word as Word
import qualified Numeric.Natural as Natural
@ -125,18 +128,15 @@ class Cast source target where
default cast :: Coerce.Coercible source target => source -> target
cast = Coerce.coerce
-- https://twitter.com/BanjoTragedy/status/1329091174305447938
type family Ambiguous a where
Ambiguous Void.Void = ()
Ambiguous a = a
type Ambiguous a b = (Type.==) a b ~ 'True
-- | TODO
from :: forall s target source . (Ambiguous s ~ source, Cast source target) => source -> target
from :: forall s target source . (Ambiguous s source, Cast source target) => source -> target
from = cast
-- | This function converts a value from one type into another. This is the
-- same as 'cast' except that the type variables are in the opposite order.
into :: forall t source target . (Ambiguous t ~ target, Cast source target) => source -> target
into :: forall t source target . (Ambiguous t target, Cast source target) => source -> target
into = cast
-- | This function converts a value from one type into another by going through