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{-
(c) The University of Glasgow 2006
(c) The GRASP/AQUA Project, Glasgow University, 1992-1998
-}
{-# LANGUAGE CPP #-}
{-# LANGUAGE DeriveFunctor #-}
{-# LANGUAGE PatternSynonyms #-}
{-# LANGUAGE BangPatterns #-}
#if !defined(GHC_LOADED_INTO_GHCI)
{-# LANGUAGE UnboxedTuples #-}
#endif
module UniqSupply (
-- * Main data type
UniqSupply, -- Abstractly
-- ** Operations on supplies
uniqFromSupply, uniqsFromSupply, -- basic ops
takeUniqFromSupply, uniqFromMask,
mkSplitUniqSupply,
splitUniqSupply, listSplitUniqSupply,
-- * Unique supply monad and its abstraction
UniqSM, MonadUnique(..),
-- ** Operations on the monad
initUs, initUs_,
-- * Set supply strategy
initUniqSupply
) where
import GhcPrelude
import Unique
import PlainPanic (panic)
import GHC.IO
import MonadUtils
import Control.Monad
import Data.Bits
import Data.Char
import Control.Monad.Fail as Fail
#include "Unique.h"
{-
************************************************************************
* *
\subsection{Splittable Unique supply: @UniqSupply@}
* *
************************************************************************
-}
-- | Unique Supply
--
-- 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 {-# UNPACK #-} !Int -- make the Unique with this
UniqSupply UniqSupply
-- when split => these two supplies
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
takeUniqFromSupply :: UniqSupply -> (Unique, UniqSupply)
-- ^ Obtain the 'Unique' from this particular 'UniqSupply', and a new supply
uniqFromMask :: Char -> IO Unique
uniqFromMask mask
= do { uqNum <- genSym
; return $! mkUnique mask uqNum }
mkSplitUniqSupply c
= case ord c `shiftL` uNIQUE_BITS of
!mask -> let
-- here comes THE MAGIC:
-- This is one of the most hammered bits in the whole compiler
mk_supply
-- NB: Use unsafeInterleaveIO for thread-safety.
= unsafeInterleaveIO (
genSym >>= \ u ->
mk_supply >>= \ s1 ->
mk_supply >>= \ s2 ->
return (MkSplitUniqSupply (mask .|. u) s1 s2)
)
in
mk_supply
foreign import ccall unsafe "genSym" genSym :: IO Int
foreign import ccall unsafe "initGenSym" initUniqSupply :: Int -> Int -> IO ()
splitUniqSupply (MkSplitUniqSupply _ s1 s2) = (s1, s2)
listSplitUniqSupply (MkSplitUniqSupply _ s1 s2) = s1 : listSplitUniqSupply s2
uniqFromSupply (MkSplitUniqSupply n _ _) = mkUniqueGrimily n
uniqsFromSupply (MkSplitUniqSupply n _ s2) = mkUniqueGrimily n : uniqsFromSupply s2
takeUniqFromSupply (MkSplitUniqSupply n s1 _) = (mkUniqueGrimily n, s1)
{-
************************************************************************
* *
\subsubsection[UniqSupply-monad]{@UniqSupply@ monad: @UniqSM@}
* *
************************************************************************
-}
-- Avoids using unboxed tuples when loading into GHCi
#if !defined(GHC_LOADED_INTO_GHCI)
type UniqResult result = (# result, UniqSupply #)
pattern UniqResult :: a -> b -> (# a, b #)
pattern UniqResult x y = (# x, y #)
{-# COMPLETE UniqResult #-}
#else
data UniqResult result = UniqResult !result {-# UNPACK #-} !UniqSupply
deriving (Functor)
#endif
-- | A monad which just gives the ability to obtain 'Unique's
newtype UniqSM result = USM { unUSM :: UniqSupply -> UniqResult result }
deriving (Functor)
instance Monad UniqSM where
(>>=) = thenUs
(>>) = (*>)
instance Applicative UniqSM where
pure = returnUs
(USM f) <*> (USM x) = USM $ \us0 -> case f us0 of
UniqResult ff us1 -> case x us1 of
UniqResult xx us2 -> UniqResult (ff xx) us2
(*>) = thenUs_
-- TODO: try to get rid of this instance
instance Fail.MonadFail UniqSM where
fail = panic
-- | Run the 'UniqSM' action, returning the final 'UniqSupply'
initUs :: UniqSupply -> UniqSM a -> (a, UniqSupply)
initUs init_us m = case unUSM m init_us of { UniqResult 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 { UniqResult r _ -> r }
{-# INLINE thenUs #-}
{-# INLINE returnUs #-}
{-# INLINE splitUniqSupply #-}
-- @thenUs@ is where we split the @UniqSupply@.
liftUSM :: UniqSM a -> UniqSupply -> (a, UniqSupply)
liftUSM (USM m) us0 = case m us0 of UniqResult a us1 -> (a, us1)
instance MonadFix UniqSM where
mfix m = USM (\us0 -> let (r,us1) = liftUSM (m r) us0 in UniqResult r us1)
thenUs :: UniqSM a -> (a -> UniqSM b) -> UniqSM b
thenUs (USM expr) cont
= USM (\us0 -> case (expr us0) of
UniqResult result us1 -> unUSM (cont result) us1)
thenUs_ :: UniqSM a -> UniqSM b -> UniqSM b
thenUs_ (USM expr) (USM cont)
= USM (\us0 -> case (expr us0) of { UniqResult _ us1 -> cont us1 })
returnUs :: a -> UniqSM a
returnUs result = USM (\us -> UniqResult result us)
getUs :: UniqSM UniqSupply
getUs = USM (\us0 -> case splitUniqSupply us0 of (us1,us2) -> UniqResult us1 us2)
-- | 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]
-- This default definition of getUniqueM, while correct, is not as
-- efficient as it could be since it needlessly generates and throws away
-- an extra Unique. For your instances consider providing an explicit
-- definition for 'getUniqueM' which uses 'takeUniqFromSupply' directly.
getUniqueM = liftM uniqFromSupply getUniqueSupplyM
getUniquesM = liftM uniqsFromSupply getUniqueSupplyM
instance MonadUnique UniqSM where
getUniqueSupplyM = getUs
getUniqueM = getUniqueUs
getUniquesM = getUniquesUs
getUniqueUs :: UniqSM Unique
getUniqueUs = USM (\us0 -> case takeUniqFromSupply us0 of
(u,us1) -> UniqResult u us1)
getUniquesUs :: UniqSM [Unique]
getUniquesUs = USM (\us0 -> case splitUniqSupply us0 of
(us1,us2) -> UniqResult (uniqsFromSupply us1) us2)
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