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Merged
garyb merged 2 commits into from
Nov 30, 2018
Merged

Reorder Inject instances to allow inj :: f ~> f #19

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2a0a652
Reorder Inject instances to allow inj :: f ~> f
garyb Nov 30, 2018
772bc67
Add injection tests
garyb Nov 30, 2018
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10 changes: 5 additions & 5 deletions src/Data/Functor/Coproduct/Inject.purs
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Original file line number Diff line number Diff line change
Expand Up @@ -10,14 +10,14 @@ class Inject f g where
inj :: forall a. f a -> g a
prj :: forall a. g a -> Maybe (f a)

instance injectLeft :: Inject f (Coproduct f g) where
instance injectReflexive :: Inject f f where
inj = identity
prj = Just

else instance injectLeft :: Inject f (Coproduct f g) where
inj = Coproduct <<< Left
prj = coproduct Just (const Nothing)

else instance injectRight :: Inject f g => Inject f (Coproduct h g) where
inj = Coproduct <<< Right <<< inj
prj = coproduct (const Nothing) prj

else instance injectReflexive :: Inject f f where
inj = identity
prj = Just
23 changes: 23 additions & 0 deletions test/Main.purs
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Expand Up @@ -2,14 +2,22 @@ module Test.Main where

import Prelude

import Data.Const (Const)
import Data.Functor.Compose (Compose(..))
import Data.Functor.Coproduct (Coproduct, left, right)
import Data.Functor.Coproduct.Inject (inj)
import Data.Identity (Identity(..))
import Data.Maybe (Maybe(..))
import Effect (Effect)
import Test.Assert (assertEqual)

main :: Effect Unit
main = do
testComposeOrdering
testInjections

testComposeOrdering :: Effect Unit
testComposeOrdering = do
assertEqual
{ expected: Compose (Identity (Just true))
, actual: Compose (Identity (Just true))
Expand All @@ -18,3 +26,18 @@ main = do
{ expected: Compose (Identity (Just true)) > Compose (Identity (Just false))
, actual: true
}

testInjections :: Effect Unit
testInjections = do
assertEqual
{ expected: Identity unit
, actual: inj (Identity unit)
}
assertEqual
{ expected: left (Identity unit) :: Coproduct Identity (Const Void) Unit
, actual: inj (Identity unit)
}
assertEqual
{ expected: right (Identity unit) :: Coproduct (Const Void) Identity Unit
, actual: inj (Identity unit)
}