mirror of
https://github.com/polysemy-research/polysemy.git
synced 2024-09-11 02:25:43 +03:00
Add insertAt
A combinator that allows adding effects at a specified index into the effect stack
This commit is contained in:
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@ -4,6 +4,7 @@
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* Deprecate `traceToIO` and replace it with `traceToStdout` and `traceToStderr`
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* Support GHC 9.0.1
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* Added the combinator `insertAt`, which allows adding effects at a specified index into the effect stack
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## 1.5.0.0 (2021-03-30)
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@ -80,6 +80,7 @@ test-suite polysemy-plugin-test
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BadSpec
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DoctestSpec
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ExampleSpec
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InsertSpec
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LegitimateTypeErrorSpec
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MultipleVarsSpec
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PluginSpec
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22
polysemy-plugin/test/InsertSpec.hs
Normal file
22
polysemy-plugin/test/InsertSpec.hs
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@ -0,0 +1,22 @@
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module InsertSpec where
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import Polysemy.State (State)
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import Polysemy.Reader (Reader)
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import Polysemy.Internal (insertAt)
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import Polysemy
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import Test.Hspec
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insertAtWithIndex :: Sem (e1 : e2 : e3 : e4 : r) a -> Sem (e1 : e2 : Reader i : e3 : e4 : r) a
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insertAtWithIndex = insertAt @2
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insertAtAndRaiseUnder :: Sem (e1 : r) a -> Sem (e1 : e2 : State s : e3 : Reader i : e4 : r) a
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insertAtAndRaiseUnder = raise2Under . insertAt @2 . raiseUnder
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insertAtEmpty :: Sem (e1 : e2 : r) a -> Sem (e1 : e2 : r) a
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insertAtEmpty = insertAt @2
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spec :: Spec
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spec = parallel $ do
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describe "insert" $ do
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it "insert" $ do
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1 `shouldBe` 1
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@ -9,6 +9,7 @@ module TypeErrors where
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-- >>> :set -fplugin=Polysemy.Plugin
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-- >>> :m +Polysemy
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-- >>> :m +Polysemy.State
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-- >>> :m +Polysemy.Reader
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-- >>> :m +Data.Maybe
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@ -26,3 +27,50 @@ module TypeErrors where
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-- ...
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missingFmap = ()
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--------------------------------------------------------------------------------
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-- |
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-- >>> :{
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-- insertSome :: ∀ e1 e2 s r a . Sem (e1 ': e2 ': r) a -> Sem (e1 ': e2 ': State s ': r) a
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-- insertSome = insertAt
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-- :}
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-- ...
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-- ... insertAt: You must provide the index ...
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-- ...
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insertAtUnprovidedIndex = ()
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--------------------------------------------------------------------------------
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-- |
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-- >>> :{
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-- insertSome :: Sem (e1 : e2 : e3 : e4 : r) a -> Sem (e1 : e2 : Reader i : e3 : e4 : r) a
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-- insertSome = insertAt @1
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-- :}
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-- ...
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-- ...insertAt: Failed to insert effects at index 1
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-- ...
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-- ... before ...
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-- ...'[e1]
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-- ... after ...
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-- ...e2 : e3 : e4 : r
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-- ...Actual ...
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-- ...e1 : e2 : Reader i : e3 : e4 : r
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-- ...
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insertAtWrongIndex = ()
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--------------------------------------------------------------------------------
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-- |
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-- Note: The /Actual/ row doesn't match the return type because of the 'raiseUnder'.
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-- >>> :{
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-- insertSome :: Sem (e1 : r) a -> Sem (e1 : e2 : State s : e3 : Reader i : e4 : r) a
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-- insertSome = raiseUnder . insertAt @2 . raise2Under
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-- :}
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-- ...
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-- ...insertAt: Failed to insert effects at index 2
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-- ...
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-- ... before ...
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-- ...'[e1, State s]
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-- ... after ...
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-- ...e30 : r0
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-- ...Actual ...
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-- ...e1 : State s : e3 : Reader i : e4 : r
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-- ...
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insertAtAndRaiseWrongIndex = ()
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@ -62,8 +62,10 @@ library
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Polysemy.Internal.CustomErrors.Redefined
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Polysemy.Internal.Fixpoint
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Polysemy.Internal.Forklift
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Polysemy.Internal.Index
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Polysemy.Internal.Kind
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Polysemy.Internal.NonDet
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Polysemy.Internal.Sing
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Polysemy.Internal.Strategy
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Polysemy.Internal.Tactics
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Polysemy.Internal.TH.Common
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@ -35,6 +35,7 @@ module Polysemy
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, raise3Under
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, raise_
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, subsume_
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, insertAt
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-- * Trivial Interpretation
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, subsume
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@ -9,13 +9,13 @@ module Polysemy.Bundle
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, runBundle
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, subsumeBundle
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-- * Miscellaneous
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, KnownList
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) where
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import Polysemy
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import Polysemy.Internal
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import Polysemy.Internal.Bundle
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import Polysemy.Internal.Union
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import Polysemy.Internal.Bundle (subsumeMembership)
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import Polysemy.Internal.Sing (KnownList (singList))
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------------------------------------------------------------------------------
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-- | An effect for collecting multiple effects into one effect.
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@ -58,8 +58,8 @@ runBundle
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-> Sem (Append r' r) a
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runBundle = hoistSem $ \u -> hoist runBundle $ case decomp u of
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Right (Weaving (Bundle pr e) s wv ex ins) ->
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Union (extendMembership @_ @r pr) $ Weaving e s wv ex ins
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Left g -> weakenList @r' @r g
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Union (extendMembershipRight @r' @r pr) $ Weaving e s wv ex ins
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Left g -> weakenList @r' @r (singList @r') g
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{-# INLINE runBundle #-}
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------------------------------------------------------------------------------
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@ -30,6 +30,7 @@ module Polysemy.Internal
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, Subsume (..)
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, subsume
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, subsumeUsing
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, insertAt
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, Embed (..)
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, usingSem
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, liftSem
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@ -44,6 +45,8 @@ module Polysemy.Internal
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import Control.Applicative
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import Control.Monad
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#if __GLASGOW_HASKELL__ < 808
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import Control.Monad.Fail
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#endif
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import Control.Monad.Fix
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@ -53,10 +56,13 @@ import Data.Kind
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import Polysemy.Embed.Type
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import Polysemy.Fail.Type
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import Polysemy.Internal.Fixpoint
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import Polysemy.Internal.Index (InsertAtUnprovidedIndex, InsertAtIndex(insertAtIndex))
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import Polysemy.Internal.Kind
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import Polysemy.Internal.NonDet
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import Polysemy.Internal.PluginLookup
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import Polysemy.Internal.Union
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import Type.Errors (WhenStuck)
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import Polysemy.Internal.Sing (ListOfLength (listOfLength))
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-- $setup
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@ -540,6 +546,32 @@ subsumeUsing pr =
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go
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{-# INLINE subsumeUsing #-}
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------------------------------------------------------------------------------
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-- | Introduce a set of effects into 'Sem' at the index @i@, before the effect
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-- that previously occupied that position. This is intended to be used with a
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-- type application:
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--
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-- @
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-- let
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-- sem1 :: Sem [e1, e2, e3, e4, e5] a
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-- sem1 = insertAt @2 (sem0 :: Sem [e1, e2, e5] a)
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-- @
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--
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-- @since 1.6.0.0
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insertAt
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:: forall index inserted head oldTail tail old full a
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. ( ListOfLength index head
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, WhenStuck index InsertAtUnprovidedIndex
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, old ~ Append head oldTail
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, tail ~ Append inserted oldTail
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, full ~ Append head tail
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, InsertAtIndex index head tail oldTail full inserted)
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=> Sem old a
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-> Sem full a
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insertAt = hoistSem $ \u -> hoist (insertAt @index @inserted @head @oldTail) $
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weakenMid @oldTail (listOfLength @index @head) (insertAtIndex @Effect @index @head @tail @oldTail @full @inserted) u
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{-# INLINE insertAt #-}
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------------------------------------------------------------------------------
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-- | Embed an effect into a 'Sem'. This is used primarily via
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@ -588,11 +620,6 @@ runM (Sem m) = m $ \z ->
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{-# INLINE runM #-}
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type family Append l r where
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Append (a ': l) r = a ': (Append l r)
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Append '[] r = r
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------------------------------------------------------------------------------
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-- | Type synonym for interpreters that consume an effect without changing the
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-- return value. Offered for user convenience.
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@ -2,15 +2,11 @@
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{-# OPTIONS_HADDOCK not-home #-}
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module Polysemy.Internal.Bundle (
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module Polysemy.Internal.Bundle,
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Append,
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) where
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module Polysemy.Internal.Bundle where
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import Data.Proxy
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import Polysemy
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import Polysemy.Internal (Append)
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import Polysemy.Internal.Union
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import Polysemy (Members)
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import Polysemy.Internal.Union (ElemOf(..), membership)
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import Polysemy.Internal.Kind (Append)
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extendMembership :: forall r r' e. ElemOf e r -> ElemOf e (Append r r')
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extendMembership Here = Here
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@ -21,35 +17,3 @@ subsumeMembership :: forall r r' e. Members r r' => ElemOf e r -> ElemOf e r'
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subsumeMembership Here = membership @e @r'
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subsumeMembership (There (pr :: ElemOf e r'')) = subsumeMembership @r'' @r' pr
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{-# INLINE subsumeMembership #-}
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weakenList :: forall r' r m a
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. KnownList r'
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=> Union r m a
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-> Union (Append r' r) m a
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weakenList u = unconsKnownList @_ @r' u (\_ (_ :: Proxy r'') -> weaken (weakenList @r'' u))
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{-# INLINE weakenList #-}
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------------------------------------------------------------------------------
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-- | A class for type-level lists with a known spine.
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--
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-- This constraint is eventually satisfied as @r@ is instantied to a
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-- concrete list.
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class KnownList (l :: [k]) where
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unconsKnownList :: (l ~ '[] => a)
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-> ( forall x r
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. (l ~ (x ': r), KnownList r)
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=> Proxy x
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-> Proxy r
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-> a
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)
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-> a
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instance KnownList '[] where
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unconsKnownList b _ = b
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{-# INLINE unconsKnownList #-}
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instance KnownList r => KnownList (x ': r) where
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unconsKnownList _ b = b Proxy Proxy
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{-# INLINE unconsKnownList #-}
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55
src/Polysemy/Internal/Index.hs
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55
src/Polysemy/Internal/Index.hs
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@ -0,0 +1,55 @@
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{-# LANGUAGE AllowAmbiguousTypes #-}
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{-# LANGUAGE UndecidableInstances #-}
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{-# LANGUAGE FlexibleInstances #-}
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{-# LANGUAGE MultiParamTypeClasses #-}
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{-# OPTIONS_HADDOCK not-home #-}
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module Polysemy.Internal.Index where
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import GHC.TypeLits (Nat)
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import Type.Errors (TypeError, ErrorMessage(ShowType))
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import Type.Errors.Pretty (type (<>), type (%))
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import Polysemy.Internal.Sing (SList (SEnd, SCons))
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------------------------------------------------------------------------------
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-- | Infer a partition of the result type @full@ so that for the fixed segments
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-- @head@ and @tail@, the new segment @inserted@ contains the missing effects
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-- between them.
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class InsertAtIndex (index :: Nat) (head :: [k]) (tail :: [k]) (oldTail :: [k]) (full :: [k]) (inserted :: [k]) where
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insertAtIndex :: SList inserted
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instance inserted ~ '[] => InsertAtIndex index head oldTail oldTail full inserted where
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insertAtIndex = SEnd
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{-# INLINE insertAtIndex #-}
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instance {-# INCOHERENT #-} (
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InsertAtIndex index head tail oldTail full insertedTail,
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inserted ~ (e ': insertedTail)
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) => InsertAtIndex index head (e ': tail) oldTail full inserted where
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insertAtIndex = SCons (insertAtIndex @_ @index @head @tail @oldTail @full)
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{-# INLINE insertAtIndex #-}
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instance {-# INCOHERENT #-} TypeError (InsertAtFailure index oldTail head full)
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=> InsertAtIndex index head tail oldTail full inserted where
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insertAtIndex = error "unreachable"
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type family InsertAtUnprovidedIndex where
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InsertAtUnprovidedIndex = TypeError (
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"insertAt: You must provide the index at which the effects should be inserted as a type application."
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% "Example: insertAt @5"
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)
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type InsertAtFailure index soughtTail head full =
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"insertAt: Failed to insert effects at index " <> 'ShowType index
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% "There is a mismatch between what's been determined as the head and tail between the newly inserted effects,"
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<> " and the actual desired return type."
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% "Determined head before inserted effects:"
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% "\t" <> 'ShowType head
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% "Determined tail after the inserted effects:"
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% "\t" <> 'ShowType soughtTail
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% "Actual desired return type:"
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% "\t" <> 'ShowType full
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% "Make sure that the index provided to insertAt is correct, and that the desired return type simply requires"
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<> " inserting effects."
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@ -1,6 +1,8 @@
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{-# OPTIONS_HADDOCK not-home #-}
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module Polysemy.Internal.Kind where
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import Data.Kind
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import Data.Kind (Type)
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------------------------------------------------------------------------------
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-- | The kind of effects.
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@ -14,3 +16,7 @@ type Effect = (Type -> Type) -> Type -> Type
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-- @since 0.5.0.0
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type EffectRow = [Effect]
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type family Append l r where
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Append (a ': l) r = a ': (Append l r)
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Append '[] r = r
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37
src/Polysemy/Internal/Sing.hs
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37
src/Polysemy/Internal/Sing.hs
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@ -0,0 +1,37 @@
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{-# LANGUAGE MultiParamTypeClasses #-}
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{-# LANGUAGE FlexibleInstances #-}
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{-# LANGUAGE UndecidableInstances #-}
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{-# LANGUAGE AllowAmbiguousTypes #-}
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{-# OPTIONS_HADDOCK not-home #-}
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module Polysemy.Internal.Sing where
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import GHC.TypeLits (type (-), Nat)
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import Polysemy.Internal.Kind (Effect)
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data SList l where
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SEnd :: SList '[]
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SCons :: SList xs -> SList (x ': xs)
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class KnownList l where
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singList :: SList l
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instance KnownList '[] where
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singList = SEnd
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{-# INLINE singList #-}
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instance KnownList xs => KnownList (x ': xs) where
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singList = SCons singList
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{-# INLINE singList #-}
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class ListOfLength (n :: Nat) (l :: [Effect]) where
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listOfLength :: SList l
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instance {-# OVERLAPPING #-} (l ~ '[]) => ListOfLength 0 l where
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listOfLength = SEnd
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{-# INLINE listOfLength #-}
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instance (ListOfLength (n - 1) xs, l ~ (x ': xs)) => ListOfLength n l where
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listOfLength = SCons (listOfLength @(n - 1))
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{-# INLINE listOfLength #-}
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@ -39,7 +39,11 @@ module Polysemy.Internal.Union
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-- * Checking membership
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, KnownRow
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, tryMembership
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) where
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, extendMembershipLeft
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, extendMembershipRight
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, injectMembership
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, weakenList
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, weakenMid) where
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import Control.Monad
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import Data.Functor.Compose
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@ -48,6 +52,7 @@ import Data.Kind
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import Data.Typeable
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import Polysemy.Internal.Kind
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import {-# SOURCE #-} Polysemy.Internal
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import Polysemy.Internal.Sing (SList (SEnd, SCons))
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#ifndef NO_ERROR_MESSAGES
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import Polysemy.Internal.CustomErrors
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@ -251,6 +256,41 @@ tryMembership :: forall e r. (Typeable e, KnownRow r) => Maybe (ElemOf e r)
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tryMembership = tryMembership' @r @e
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{-# INLINE tryMembership #-}
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------------------------------------------------------------------------------
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-- | Extends a proof that @e@ is an element of @r@ to a proof that @e@ is an
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-- element of the concatenation of the lists @l@ and @r@.
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-- @l@ must be specified as a singleton list proof.
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extendMembershipLeft :: forall l r e. SList l -> ElemOf e r -> ElemOf e (Append l r)
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extendMembershipLeft SEnd pr = pr
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extendMembershipLeft (SCons l) pr = There (extendMembershipLeft l pr)
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{-# INLINE extendMembershipLeft #-}
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------------------------------------------------------------------------------
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-- | Extends a proof that @e@ is an element of @l@ to a proof that @e@ is an
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-- element of the concatenation of the lists @l@ and @r@.
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extendMembershipRight :: forall l r e. ElemOf e l -> ElemOf e (Append l r)
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extendMembershipRight Here = Here
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extendMembershipRight (There e) = There (extendMembershipRight @_ @r e)
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{-# INLINE extendMembershipRight #-}
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------------------------------------------------------------------------------
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-- | Extends a proof that @e@ is an element of @left <> right@ to a proof that
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-- @e@ is an element of @left <> mid <> right@.
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-- Both @left@ and @right@ must be specified as singleton list proofs.
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injectMembership :: forall right e left mid
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. SList left
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-> SList mid
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-> ElemOf e (Append left right)
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-> ElemOf e (Append left (Append mid right))
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injectMembership SEnd sm pr = extendMembershipLeft sm pr
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injectMembership (SCons _) _ Here = Here
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injectMembership (SCons sl) sm (There pr) = There (injectMembership @right sl sm pr)
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{-# INLINE injectMembership #-}
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------------------------------------------------------------------------------
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-- | Decompose a 'Union'. Either this union contains an effect @e@---the head
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-- of the @r@ list---or it doesn't.
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@ -282,12 +322,32 @@ absurdU = \case {}
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------------------------------------------------------------------------------
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-- | Weaken a 'Union' so it is capable of storing a new sort of effect.
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-- | Weaken a 'Union' so it is capable of storing a new sort of effect at the
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-- head.
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weaken :: forall e r m a. Union r m a -> Union (e ': r) m a
|
||||
weaken (Union pr a) = Union (There pr) a
|
||||
{-# INLINE weaken #-}
|
||||
|
||||
|
||||
------------------------------------------------------------------------------
|
||||
-- | Weaken a 'Union' so it is capable of storing a number of new effects at
|
||||
-- the head, specified as a singleton list proof.
|
||||
weakenList :: SList l -> Union r m a -> Union (Append l r) m a
|
||||
weakenList sl (Union pr e) = Union (extendMembershipLeft sl pr) e
|
||||
{-# INLINE weakenList #-}
|
||||
|
||||
|
||||
------------------------------------------------------------------------------
|
||||
-- | Weaken a 'Union' so it is capable of storing a number of new effects
|
||||
-- somewhere within the previous effect list.
|
||||
-- Both the prefix and the new effects are specified as singleton list proofs.
|
||||
weakenMid :: forall right m a left mid
|
||||
. SList left -> SList mid
|
||||
-> Union (Append left right) m a
|
||||
-> Union (Append left (Append mid right)) m a
|
||||
weakenMid sl sm (Union pr e) = Union (injectMembership @right sl sm pr) e
|
||||
{-# INLINE weakenMid #-}
|
||||
|
||||
|
||||
------------------------------------------------------------------------------
|
||||
-- | Lift an effect @e@ into a 'Union' capable of holding it.
|
||||
|
Loading…
Reference in New Issue
Block a user