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{-# OPTIONS_GHC -ddump-rule-firings -ddump-simpl
-dsuppress-coercions -dsuppress-uniques #-}
{-# LANGUAGE Arrows #-}
module T18013 where
import Control.Arrow
import T18013a
-- We want to ensure this generates good code. Uses of (.) should be
-- specialized and inlined, and the rules defined on mkRule should fire.
mapMaybeRule :: Rule IO a b -> Rule IO (Maybe a) (Maybe b)
mapMaybeRule f = proc v -> case v of
Just x -> do
y <- f -< x
returnA -< Just y
Nothing -> returnA -< Nothing
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