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%
% (c) The University of Glasgow 2006
% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\begin{code}
module UniqSupply (
-- * Main data type
UniqSupply, -- Abstractly
-- ** Operations on supplies
uniqFromSupply, uniqsFromSupply, -- basic ops
mkSplitUniqSupply,
splitUniqSupply, listSplitUniqSupply,
-- * Unique supply monad and its abstraction
UniqSM, MonadUnique(..),
-- ** Operations on the monad
initUs, initUs_,
lazyThenUs, lazyMapUs,
-- ** Deprecated operations on 'UniqSM'
getUniqueUs, getUs, returnUs, thenUs, mapUs
) where
import Unique
import FastTypes
import MonadUtils
import Control.Monad
import Control.Monad.Fix
#if __GLASGOW_HASKELL__ >= 607
import GHC.IOBase (unsafeDupableInterleaveIO)
#else
import System.IO.Unsafe ( unsafeInterleaveIO )
unsafeDupableInterleaveIO :: IO a -> IO a
unsafeDupableInterleaveIO = unsafeInterleaveIO
#endif
\end{code}
%************************************************************************
%* *
\subsection{Splittable Unique supply: @UniqSupply@}
%* *
%************************************************************************
\begin{code}
-- | A value of type 'UniqSupply' is unique, and it can
-- supply /one/ distinct 'Unique'. Also, from the supply, one can
-- also manufacture an arbitrary number of further 'UniqueSupply' values,
-- which will be distinct from the first and from all others.
data UniqSupply
= MkSplitUniqSupply FastInt -- make the Unique with this
UniqSupply UniqSupply
-- when split => these two supplies
\end{code}
\begin{code}
mkSplitUniqSupply :: Char -> IO UniqSupply
-- ^ Create a unique supply out of thin air. The character given must
-- be distinct from those of all calls to this function in the compiler
-- for the values generated to be truly unique.
splitUniqSupply :: UniqSupply -> (UniqSupply, UniqSupply)
-- ^ Build two 'UniqSupply' from a single one, each of which
-- can supply its own 'Unique'.
listSplitUniqSupply :: UniqSupply -> [UniqSupply]
-- ^ Create an infinite list of 'UniqSupply' from a single one
uniqFromSupply :: UniqSupply -> Unique
-- ^ Obtain the 'Unique' from this particular 'UniqSupply'
uniqsFromSupply :: UniqSupply -> [Unique] -- Infinite
-- ^ Obtain an infinite list of 'Unique' that can be generated by constant splitting of the supply
\end{code}
\begin{code}
mkSplitUniqSupply c
= case fastOrd (cUnbox c) `shiftLFastInt` _ILIT(24) of
mask -> let
-- here comes THE MAGIC:
-- This is one of the most hammered bits in the whole compiler
mk_supply
= unsafeDupableInterleaveIO (
genSymZh >>= \ u_ -> case iUnbox u_ of { u -> (
mk_supply >>= \ s1 ->
mk_supply >>= \ s2 ->
return (MkSplitUniqSupply (mask `bitOrFastInt` u) s1 s2)
)})
in
mk_supply
foreign import ccall unsafe "genSymZh" genSymZh :: IO Int
splitUniqSupply (MkSplitUniqSupply _ s1 s2) = (s1, s2)
listSplitUniqSupply (MkSplitUniqSupply _ s1 s2) = s1 : listSplitUniqSupply s2
\end{code}
\begin{code}
uniqFromSupply (MkSplitUniqSupply n _ _) = mkUniqueGrimily (iBox n)
uniqsFromSupply (MkSplitUniqSupply n _ s2) = mkUniqueGrimily (iBox n) : uniqsFromSupply s2
\end{code}
%************************************************************************
%* *
\subsubsection[UniqSupply-monad]{@UniqSupply@ monad: @UniqSM@}
%* *
%************************************************************************
\begin{code}
-- | A monad which just gives the ability to obtain 'Unique's
newtype UniqSM result = USM { unUSM :: UniqSupply -> (result, UniqSupply) }
instance Monad UniqSM where
return = returnUs
(>>=) = thenUs
(>>) = thenUs_
instance Functor UniqSM where
fmap f (USM x) = USM (\us -> case x us of
(r, us') -> (f r, us'))
instance Applicative UniqSM where
pure = returnUs
(USM f) <*> (USM x) = USM $ \us -> case f us of
(ff, us') -> case x us' of
(xx, us'') -> (ff xx, us'')
-- | Run the 'UniqSM' action, returning the final 'UniqSupply'
initUs :: UniqSupply -> UniqSM a -> (a, UniqSupply)
initUs init_us m = case unUSM m init_us of { (r,us) -> (r,us) }
-- | Run the 'UniqSM' action, discarding the final 'UniqSupply'
initUs_ :: UniqSupply -> UniqSM a -> a
initUs_ init_us m = case unUSM m init_us of { (r, _) -> r }
{-# INLINE thenUs #-}
{-# INLINE lazyThenUs #-}
{-# INLINE returnUs #-}
{-# INLINE splitUniqSupply #-}
\end{code}
@thenUs@ is where we split the @UniqSupply@.
\begin{code}
instance MonadFix UniqSM where
mfix m = USM (\us -> let (r,us') = unUSM (m r) us in (r,us'))
thenUs :: UniqSM a -> (a -> UniqSM b) -> UniqSM b
thenUs (USM expr) cont
= USM (\us -> case (expr us) of
(result, us') -> unUSM (cont result) us')
lazyThenUs :: UniqSM a -> (a -> UniqSM b) -> UniqSM b
lazyThenUs (USM expr) cont
= USM (\us -> let (result, us') = expr us in unUSM (cont result) us')
thenUs_ :: UniqSM a -> UniqSM b -> UniqSM b
thenUs_ (USM expr) (USM cont)
= USM (\us -> case (expr us) of { (_, us') -> cont us' })
returnUs :: a -> UniqSM a
returnUs result = USM (\us -> (result, us))
getUs :: UniqSM UniqSupply
getUs = USM (\us -> splitUniqSupply us)
-- | A monad for generating unique identifiers
class Monad m => MonadUnique m where
-- | Get a new UniqueSupply
getUniqueSupplyM :: m UniqSupply
-- | Get a new unique identifier
getUniqueM :: m Unique
-- | Get an infinite list of new unique identifiers
getUniquesM :: m [Unique]
getUniqueM = liftM uniqFromSupply getUniqueSupplyM
getUniquesM = liftM uniqsFromSupply getUniqueSupplyM
instance MonadUnique UniqSM where
getUniqueSupplyM = USM (\us -> splitUniqSupply us)
getUniqueM = getUniqueUs
getUniquesM = getUniquesUs
getUniqueUs :: UniqSM Unique
getUniqueUs = USM (\us -> case splitUniqSupply us of
(us1,us2) -> (uniqFromSupply us1, us2))
getUniquesUs :: UniqSM [Unique]
getUniquesUs = USM (\us -> case splitUniqSupply us of
(us1,us2) -> (uniqsFromSupply us1, us2))
mapUs :: (a -> UniqSM b) -> [a] -> UniqSM [b]
mapUs _ [] = returnUs []
mapUs f (x:xs)
= f x `thenUs` \ r ->
mapUs f xs `thenUs` \ rs ->
returnUs (r:rs)
\end{code}
\begin{code}
-- {-# SPECIALIZE mapM :: (a -> UniqSM b) -> [a] -> UniqSM [b] #-}
-- {-# SPECIALIZE mapAndUnzipM :: (a -> UniqSM (b,c)) -> [a] -> UniqSM ([b],[c]) #-}
-- {-# SPECIALIZE mapAndUnzip3M :: (a -> UniqSM (b,c,d)) -> [a] -> UniqSM ([b],[c],[d]) #-}
lazyMapUs :: (a -> UniqSM b) -> [a] -> UniqSM [b]
lazyMapUs _ [] = returnUs []
lazyMapUs f (x:xs)
= f x `lazyThenUs` \ r ->
lazyMapUs f xs `lazyThenUs` \ rs ->
returnUs (r:rs)
\end{code}
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