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Propagate Par errors #56

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Merged
merged 1 commit into from
Jun 2, 2016
Merged

Propagate Par errors #56

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11 changes: 7 additions & 4 deletions src/Control/Monad/Aff/Par.purs
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Original file line number Diff line number Diff line change
Expand Up @@ -11,10 +11,11 @@ import Prelude
import Control.Alt (Alt)
import Control.Alternative (Alternative)
import Control.Monad.Aff (attempt, cancelWith, forkAff)
import Control.Monad.Aff.AVar (AffAVar(), makeVar, makeVar', takeVar, putVar, killVar)
import Control.Monad.Aff.AVar (AffAVar(), AVar(), makeVar, makeVar', takeVar, putVar, killVar)
import Control.Monad.Eff.Exception (Error())
import Control.Plus (Plus, empty)

import Data.Either (either)
import Data.Either (Either(), either)
import Data.Monoid (Monoid, mempty)

newtype Par e a = Par (AffAVar e a)
Expand All @@ -34,10 +35,12 @@ instance functorPar :: Functor (Par e) where

instance applyPar :: Apply (Par e) where
apply (Par ff) (Par fa) = Par do
let putOrKill :: forall b. AVar b -> Either Error b -> AffAVar e Unit
putOrKill v = either (killVar v) (putVar v)
vf <- makeVar
va <- makeVar
c1 <- forkAff (ff >>= putVar vf)
c2 <- forkAff (fa >>= putVar va)
c1 <- forkAff (attempt ff >>= putOrKill vf)
c2 <- forkAff (attempt fa >>= putOrKill va)
(takeVar vf <*> takeVar va) `cancelWith` (c1 <> c2)

instance applicativePar :: Applicative (Par e) where
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8 changes: 8 additions & 0 deletions test/Test/Main.purs
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Expand Up @@ -86,6 +86,11 @@ test_parRace = do
Par (later' 200 $ pure "Failure: Late bird got the worm"))
log s

test_parError :: TestAVar Unit
test_parError = do
e <- attempt $ runPar (Par (throwError (error ("Oh noes!"))) *> pure unit)
either (const $ log "Success: Exception propagated") (const $ log "Failure: Exception missing") e

test_parRaceKill1 :: TestAVar Unit
test_parRaceKill1 = do
s <- runPar (Par (later' 100 $ throwError (error ("Oh noes!"))) <|>
Expand Down Expand Up @@ -183,6 +188,9 @@ main = runAff throwException (const (pure unit)) $ do
log "Testing finally"
test_finally

log "Test Par (*>)"
test_parError

log "Testing Par (<|>)"
test_parRace

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