%
\begin{code}
-{-# OPTIONS -w #-}
--- The above warning supression flag is a temporary kludge.
--- While working on this module you are encouraged to remove it and fix
--- any warnings in the module. See
--- http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
--- for details
-
module UniqSupply (
-
+ -- * Main data type
UniqSupply, -- Abstractly
+ -- ** Operations on supplies
uniqFromSupply, uniqsFromSupply, -- basic ops
-
- UniqSM, -- type: unique supply monad
- initUs, initUs_,
- lazyThenUs, lazyMapUs,
- mapAndUnzipM,
- MonadUnique(..),
+ takeUniqFromSupply,
mkSplitUniqSupply,
splitUniqSupply, listSplitUniqSupply,
- -- Deprecated:
+ -- * 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
-#include "HsVersions.h"
-
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
+import GHC.IO (unsafeDupableInterleaveIO)
\end{code}
-
%************************************************************************
%* *
\subsection{Splittable Unique supply: @UniqSupply@}
%* *
%************************************************************************
-A value of type @UniqSupply@ is unique, and it can
-supply {\em one} distinct @Unique@. Also, from the supply, one can
-also manufacture an arbitrary number of further @UniqueSupplies@,
-which will be distinct from the first and from all others.
-
\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
\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)
-listSplitUniqSupply :: UniqSupply -> [UniqSupply] -- Infinite
+-- ^ 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
\end{code}
\begin{code}
\begin{code}
uniqFromSupply (MkSplitUniqSupply n _ _) = mkUniqueGrimily (iBox n)
uniqsFromSupply (MkSplitUniqSupply n _ s2) = mkUniqueGrimily (iBox n) : uniqsFromSupply s2
+takeUniqFromSupply (MkSplitUniqSupply n s1 _) = (mkUniqueGrimily (iBox n), s1)
\end{code}
%************************************************************************
%************************************************************************
\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
(ff, us') -> case x us' of
(xx, us'') -> (ff xx, us'')
--- the initUs function also returns the final UniqSupply; initUs_ drops it
-initUs :: UniqSupply -> UniqSM a -> (a,UniqSupply)
+-- | 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,us) -> r }
+initUs_ init_us m = case unUSM m init_us of { (r, _) -> r }
{-# INLINE thenUs #-}
{-# INLINE lazyThenUs #-}
returnUs :: a -> UniqSM a
returnUs result = USM (\us -> (result, us))
-withUs :: (UniqSupply -> (a, UniqSupply)) -> UniqSM a
-withUs f = USM (\us -> f us) -- Ha ha!
-
getUs :: UniqSM UniqSupply
getUs = USM (\us -> splitUniqSupply us)
(us1,us2) -> (uniqsFromSupply us1, us2))
mapUs :: (a -> UniqSM b) -> [a] -> UniqSM [b]
-mapUs f [] = returnUs []
+mapUs _ [] = returnUs []
mapUs f (x:xs)
= f x `thenUs` \ r ->
mapUs f xs `thenUs` \ 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]) #-}
+-- {-# 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 f [] = returnUs []
+lazyMapUs _ [] = returnUs []
lazyMapUs f (x:xs)
= f x `lazyThenUs` \ r ->
lazyMapUs f xs `lazyThenUs` \ rs ->
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