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{-# OPTIONS_GHC -fglasgow-exts -O -ddump-simpl -fno-method-sharing #-}
module Roman where
import Control.Monad.ST
newtype T s a = T { unT :: Int -> ST s a }
instance Monad (T s) where
return = T . const . return
T p >>= f = T $ \i -> do { x <- p i
; unT (f x) i }
myIndex :: T s Int
{-# INLINE myIndex #-}
myIndex = T return
foo :: T s Int
foo = do { x <- myIndex
; return (x + 1) }
{- At one stage we got code looking like this:
U.a3 =
\ (@ s_a8E) (i_shA :: GHC.Base.Int) (eta_shB :: GHC.Prim.State# s_a8E) ->
case ((((U.myIndex @ s_a8E)
`cast` ...)
i_shA)
`cast` ...)
eta_shB
of wild_si5 { (# new_s_shF, r_shG #) -> ...
U.foo :: forall s_a5S. U.T s_a5S GHC.Base.Int
U.foo = U.a3 `cast` ...
The point is that myIndex should be inlined, else code is bad -}
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