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-- There was a bug in 6.12 that meant that the binding
-- for 'rght' was initially determined (correctly) to be
-- strictly demanded, but the FloatOut pass made it lazy
--
-- The test compiles the program and greps for the
-- binding of 'rght' to check that it is marked strict
-- something like this:
-- rght [Dmd=Just S] :: EvalTest.AList a
module EvalTest where
import GHC.Conc
import Control.Applicative (Applicative(..))
import Control.Monad (liftM, ap)
data Eval a = Done a
instance Functor Eval where
fmap = liftM
instance Applicative Eval where
pure = Done
(<*>) = ap
instance Monad Eval where
Done x >>= k = k x -- Note: pattern 'Done x' makes '>>=' strict
rpar :: a -> Eval a
rpar x = x `par` return x
rseq :: a -> Eval a
rseq x = x `pseq` return x
runEval :: Eval a -> a
runEval (Done x) = x
data AList a = ANil | ASing a | Append (AList a) (AList a) | AList [a]
append ANil r = r
append l ANil = l -- **
append l r = Append l r
parListTreeLike :: Integer -> Integer -> (Integer -> a) -> AList a
parListTreeLike min max fn
| max - min <= threshold = ASing (fn max)
| otherwise =
runEval $ do
rpar rght
rseq left
return (left `append` rght)
where
mid = min + ((max - min) `quot` 2)
left = parListTreeLike min mid fn
rght = parListTreeLike (mid+1) max fn
threshold = 1
|
