{-# LANGUAGE BangPatterns #-}
{-# LANGUAGE CPP #-}

-----------------------------------------------------------------------------
-- |
-- Module      :  Control.Parallel.SeqStrategies
-- Copyright   :  (c) The University of Glasgow 2001-2009
-- License     :  BSD-style (see the file libraries/base/LICENSE)
--
-- Maintainer  :  libraries@haskell.org
-- Stability   :  experimental
-- Portability :  portable
--
-- Sequential strategies provide ways to compositionally specify
-- the degree of evaluation of a data type between the extremes of
-- no evaluation and full evaluation.
-- Sequential strategies may be viewed as complimentary to the parallel
-- ones (see module "Control.Parallel.Strategies").
--

module Control.Seq
       (
         -- * The sequential strategy type
         Strategy

         -- * Application of sequential strategies
       , using            -- :: a -> Strategy a -> a
       , withStrategy     -- :: Strategy a -> a -> a

         -- * Basic sequential strategies
       , r0               -- :: Strategy a
       , rseq
       , rdeepseq         -- :: NFData a => Strategy a

         -- * Sequential strategies for lists
       , seqList          -- :: Strategy a -> Strategy [a]
       , seqListN         -- :: Int -> Strategy a -> Strategy [a]
       , seqListNth

         -- * Sequential strategies for foldable data types
       , seqFoldable      -- :: Foldable t => Strategy a -> Strategy (t a)
       , seqMap           -- :: Strategy k -> Strategy v -> Strategy (Map k v)
       , seqArray         -- :: Ix i => Strategy a -> Strategy (Array i a)
       , seqArrayBounds   -- :: Ix i => Strategy i -> Strategy (Array i a)

         -- * Sequential strategies for tuples

         -- | Evaluate the components of a tuple according to the given strategies.
         -- No guarantee is given as to the order of evaluation.

       , seqTuple2        -- :: Strategy a -> ... -> Strategy (a,...)
       , seqTuple3
       , seqTuple4
       , seqTuple5
       , seqTuple6
       , seqTuple7
       , seqTuple8
       , seqTuple9
       ) where

import Control.DeepSeq (NFData, deepseq)
#if MIN_VERSION_base(4,8,0)
import Data.Foldable (toList)
#else
import Data.Foldable (Foldable, toList)
#endif
import Data.Map (Map)
import qualified Data.Map (toList)
#if !((__GLASGOW_HASKELL__ >= 711) && MIN_VERSION_array(0,5,1))
import Data.Ix (Ix)
#endif
import Data.Array (Array)
import qualified Data.Array (bounds, elems)

infixl 0 `using`   -- lowest precedence and associate to the left

-- --------------------------------------------------------------------------
-- Sequential strategies

-- | The type @'Strategy' a@ is @a -> ()@.
-- Thus, a strategy is a function whose sole purpose it is to evaluate
-- its argument (either in full or in part).
type Strategy a = a -> ()

-- | Evaluate a value using the given strategy.
using :: a -> Strategy a -> a
a
x using :: a -> Strategy a -> a
`using` Strategy a
strat = Strategy a
strat a
x () -> a -> a
`seq` a
x

-- | Evaluate a value using the given strategy.
-- This is simply 'using' with arguments reversed.
withStrategy :: Strategy a -> a -> a
withStrategy :: Strategy a -> a -> a
withStrategy = (a -> Strategy a -> a) -> Strategy a -> a -> a
forall a b c. (a -> b -> c) -> b -> a -> c
flip a -> Strategy a -> a
forall a. a -> Strategy a -> a
using

-- --------------------------------------------------------------------------
-- Basic sequential strategies

-- | 'r0' performs *no* evaluation.
r0 :: Strategy a
r0 :: Strategy a
r0 a
_ = ()

-- | 'rseq' evaluates its argument to weak head normal form.
rseq :: Strategy a
rseq :: Strategy a
rseq a
x = a
x a -> () -> ()
`seq` ()

-- | 'rdeepseq' fully evaluates its argument.
-- Relies on class 'NFData' from module "Control.DeepSeq".
rdeepseq :: NFData a => Strategy a
rdeepseq :: Strategy a
rdeepseq a
x = a
x a -> () -> ()
forall a b. NFData a => a -> b -> b
`deepseq` ()


-- --------------------------------------------------------------------------
-- Sequential strategies for lists

-- | Evaluate each element of a list according to the given strategy.
-- This function is a specialisation of 'seqFoldable' to lists.
seqList :: Strategy a -> Strategy [a]
seqList :: Strategy a -> Strategy [a]
seqList Strategy a
_strat []    = ()
seqList Strategy a
strat (a
x:[a]
xs) = Strategy a
strat a
x () -> () -> ()
`seq` Strategy a -> Strategy [a]
forall a. Strategy a -> Strategy [a]
seqList Strategy a
strat [a]
xs
-- Alternative definition via seqFoldable:
-- seqList = seqFoldable

-- | Evaluate the first n elements of a list according to the given strategy.
seqListN :: Int -> Strategy a -> Strategy [a]
seqListN :: Int -> Strategy a -> Strategy [a]
seqListN Int
0  Strategy a
_strat [a]
_     = ()
seqListN !Int
_ Strategy a
_strat []    = ()
seqListN !Int
n Strategy a
strat (a
x:[a]
xs) = Strategy a
strat a
x () -> () -> ()
`seq` Int -> Strategy a -> Strategy [a]
forall a. Int -> Strategy a -> Strategy [a]
seqListN (Int
nInt -> Int -> Int
forall a. Num a => a -> a -> a
-Int
1) Strategy a
strat [a]
xs

-- | Evaluate the nth element of a list (if there is such) according to
-- the given strategy.
-- The spine of the list up to the nth element is evaluated as a side effect.
seqListNth :: Int -> Strategy a -> Strategy [a]
seqListNth :: Int -> Strategy a -> Strategy [a]
seqListNth Int
0  Strategy a
strat  (a
x:[a]
_)  = Strategy a
strat a
x
seqListNth !Int
_ Strategy a
_strat []     = ()
seqListNth !Int
n Strategy a
strat  (a
_:[a]
xs) = Int -> Strategy a -> Strategy [a]
forall a. Int -> Strategy a -> Strategy [a]
seqListNth (Int
nInt -> Int -> Int
forall a. Num a => a -> a -> a
-Int
1) Strategy a
strat [a]
xs


-- --------------------------------------------------------------------------
-- Sequential strategies for foldable data types

-- | Evaluate the elements of a foldable data structure according to
-- the given strategy.
seqFoldable :: Foldable t => Strategy a -> Strategy (t a)
seqFoldable :: Strategy a -> Strategy (t a)
seqFoldable Strategy a
strat = Strategy a -> Strategy [a]
forall a. Strategy a -> Strategy [a]
seqList Strategy a
strat Strategy [a] -> (t a -> [a]) -> Strategy (t a)
forall b c a. (b -> c) -> (a -> b) -> a -> c
. t a -> [a]
forall (t :: * -> *) a. Foldable t => t a -> [a]
toList
-- Alternative definition via foldl':
-- seqFoldable strat = foldl' (const strat) ()

{-# SPECIALISE seqFoldable :: Strategy a -> Strategy [a] #-}

-- | Evaluate the elements of an array according to the given strategy.
-- Evaluation of the array bounds may be triggered as a side effect.
#if (__GLASGOW_HASKELL__ >= 711) && MIN_VERSION_array(0,5,1)
seqArray :: Strategy a -> Strategy (Array i a)
#else
seqArray :: Ix i => Strategy a -> Strategy (Array i a)
#endif
seqArray :: Strategy a -> Strategy (Array i a)
seqArray Strategy a
strat = Strategy a -> Strategy [a]
forall a. Strategy a -> Strategy [a]
seqList Strategy a
strat Strategy [a] -> (Array i a -> [a]) -> Strategy (Array i a)
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Array i a -> [a]
forall i e. Array i e -> [e]
Data.Array.elems

-- | Evaluate the bounds of an array according to the given strategy.
#if (__GLASGOW_HASKELL__ >= 711) && MIN_VERSION_array(0,5,1)
seqArrayBounds :: Strategy i -> Strategy (Array i a)
#else
seqArrayBounds :: Ix i => Strategy i -> Strategy (Array i a)
#endif
seqArrayBounds :: Strategy i -> Strategy (Array i a)
seqArrayBounds Strategy i
strat = Strategy i -> Strategy i -> Strategy (i, i)
forall a b. Strategy a -> Strategy b -> Strategy (a, b)
seqTuple2 Strategy i
strat Strategy i
strat Strategy (i, i) -> (Array i a -> (i, i)) -> Strategy (Array i a)
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Array i a -> (i, i)
forall i e. Array i e -> (i, i)
Data.Array.bounds

-- | Evaluate the keys and values of a map according to the given strategies.
seqMap :: Strategy k -> Strategy v -> Strategy (Map k v)
seqMap :: Strategy k -> Strategy v -> Strategy (Map k v)
seqMap Strategy k
stratK Strategy v
stratV = Strategy (k, v) -> Strategy [(k, v)]
forall a. Strategy a -> Strategy [a]
seqList (Strategy k -> Strategy v -> Strategy (k, v)
forall a b. Strategy a -> Strategy b -> Strategy (a, b)
seqTuple2 Strategy k
stratK Strategy v
stratV) Strategy [(k, v)] -> (Map k v -> [(k, v)]) -> Strategy (Map k v)
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Map k v -> [(k, v)]
forall k a. Map k a -> [(k, a)]
Data.Map.toList


-- --------------------------------------------------------------------------
-- Sequential strategies for tuples

seqTuple2 :: Strategy a -> Strategy b -> Strategy (a,b)
seqTuple2 :: Strategy a -> Strategy b -> Strategy (a, b)
seqTuple2 Strategy a
strat1 Strategy b
strat2 (a
x1,b
x2) =
  Strategy a
strat1 a
x1 () -> () -> ()
`seq` Strategy b
strat2 b
x2

seqTuple3 :: Strategy a -> Strategy b -> Strategy c -> Strategy (a,b,c)
seqTuple3 :: Strategy a -> Strategy b -> Strategy c -> Strategy (a, b, c)
seqTuple3 Strategy a
strat1 Strategy b
strat2 Strategy c
strat3 (a
x1,b
x2,c
x3) =
  Strategy a
strat1 a
x1 () -> () -> ()
`seq` Strategy b
strat2 b
x2 () -> () -> ()
`seq` Strategy c
strat3 c
x3

seqTuple4 :: Strategy a -> Strategy b -> Strategy c -> Strategy d -> Strategy (a,b,c,d)
seqTuple4 :: Strategy a
-> Strategy b -> Strategy c -> Strategy d -> Strategy (a, b, c, d)
seqTuple4 Strategy a
strat1 Strategy b
strat2 Strategy c
strat3 Strategy d
strat4 (a
x1,b
x2,c
x3,d
x4) =
  Strategy a
strat1 a
x1 () -> () -> ()
`seq` Strategy b
strat2 b
x2 () -> () -> ()
`seq` Strategy c
strat3 c
x3 () -> () -> ()
`seq` Strategy d
strat4 d
x4

seqTuple5 :: Strategy a -> Strategy b -> Strategy c -> Strategy d -> Strategy e -> Strategy (a,b,c,d,e)
seqTuple5 :: Strategy a
-> Strategy b
-> Strategy c
-> Strategy d
-> Strategy e
-> Strategy (a, b, c, d, e)
seqTuple5 Strategy a
strat1 Strategy b
strat2 Strategy c
strat3 Strategy d
strat4 Strategy e
strat5 (a
x1,b
x2,c
x3,d
x4,e
x5) =
  Strategy a
strat1 a
x1 () -> () -> ()
`seq` Strategy b
strat2 b
x2 () -> () -> ()
`seq` Strategy c
strat3 c
x3 () -> () -> ()
`seq` Strategy d
strat4 d
x4 () -> () -> ()
`seq` Strategy e
strat5 e
x5

seqTuple6 :: Strategy a -> Strategy b -> Strategy c -> Strategy d -> Strategy e -> Strategy f -> Strategy (a,b,c,d,e,f)
seqTuple6 :: Strategy a
-> Strategy b
-> Strategy c
-> Strategy d
-> Strategy e
-> Strategy f
-> Strategy (a, b, c, d, e, f)
seqTuple6 Strategy a
strat1 Strategy b
strat2 Strategy c
strat3 Strategy d
strat4 Strategy e
strat5 Strategy f
strat6 (a
x1,b
x2,c
x3,d
x4,e
x5,f
x6) =
  Strategy a
strat1 a
x1 () -> () -> ()
`seq` Strategy b
strat2 b
x2 () -> () -> ()
`seq` Strategy c
strat3 c
x3 () -> () -> ()
`seq` Strategy d
strat4 d
x4 () -> () -> ()
`seq` Strategy e
strat5 e
x5 () -> () -> ()
`seq` Strategy f
strat6 f
x6

seqTuple7 :: Strategy a -> Strategy b -> Strategy c -> Strategy d -> Strategy e -> Strategy f -> Strategy g -> Strategy (a,b,c,d,e,f,g)
seqTuple7 :: Strategy a
-> Strategy b
-> Strategy c
-> Strategy d
-> Strategy e
-> Strategy f
-> Strategy g
-> Strategy (a, b, c, d, e, f, g)
seqTuple7 Strategy a
strat1 Strategy b
strat2 Strategy c
strat3 Strategy d
strat4 Strategy e
strat5 Strategy f
strat6 Strategy g
strat7 (a
x1,b
x2,c
x3,d
x4,e
x5,f
x6,g
x7) =
  Strategy a
strat1 a
x1 () -> () -> ()
`seq` Strategy b
strat2 b
x2 () -> () -> ()
`seq` Strategy c
strat3 c
x3 () -> () -> ()
`seq` Strategy d
strat4 d
x4 () -> () -> ()
`seq` Strategy e
strat5 e
x5 () -> () -> ()
`seq` Strategy f
strat6 f
x6 () -> () -> ()
`seq` Strategy g
strat7 g
x7

seqTuple8 :: Strategy a -> Strategy b -> Strategy c -> Strategy d -> Strategy e -> Strategy f -> Strategy g -> Strategy h -> Strategy (a,b,c,d,e,f,g,h)
seqTuple8 :: Strategy a
-> Strategy b
-> Strategy c
-> Strategy d
-> Strategy e
-> Strategy f
-> Strategy g
-> Strategy h
-> Strategy (a, b, c, d, e, f, g, h)
seqTuple8 Strategy a
strat1 Strategy b
strat2 Strategy c
strat3 Strategy d
strat4 Strategy e
strat5 Strategy f
strat6 Strategy g
strat7 Strategy h
strat8 (a
x1,b
x2,c
x3,d
x4,e
x5,f
x6,g
x7,h
x8) =
  Strategy a
strat1 a
x1 () -> () -> ()
`seq` Strategy b
strat2 b
x2 () -> () -> ()
`seq` Strategy c
strat3 c
x3 () -> () -> ()
`seq` Strategy d
strat4 d
x4 () -> () -> ()
`seq` Strategy e
strat5 e
x5 () -> () -> ()
`seq` Strategy f
strat6 f
x6 () -> () -> ()
`seq` Strategy g
strat7 g
x7 () -> () -> ()
`seq` Strategy h
strat8 h
x8

seqTuple9 :: Strategy a -> Strategy b -> Strategy c -> Strategy d -> Strategy e -> Strategy f -> Strategy g -> Strategy h -> Strategy i -> Strategy (a,b,c,d,e,f,g,h,i)
seqTuple9 :: Strategy a
-> Strategy b
-> Strategy c
-> Strategy d
-> Strategy e
-> Strategy f
-> Strategy g
-> Strategy h
-> Strategy i
-> Strategy (a, b, c, d, e, f, g, h, i)
seqTuple9 Strategy a
strat1 Strategy b
strat2 Strategy c
strat3 Strategy d
strat4 Strategy e
strat5 Strategy f
strat6 Strategy g
strat7 Strategy h
strat8 Strategy i
strat9 (a
x1,b
x2,c
x3,d
x4,e
x5,f
x6,g
x7,h
x8,i
x9) =
  Strategy a
strat1 a
x1 () -> () -> ()
`seq` Strategy b
strat2 b
x2 () -> () -> ()
`seq` Strategy c
strat3 c
x3 () -> () -> ()
`seq` Strategy d
strat4 d
x4 () -> () -> ()
`seq` Strategy e
strat5 e
x5 () -> () -> ()
`seq` Strategy f
strat6 f
x6 () -> () -> ()
`seq` Strategy g
strat7 g
x7 () -> () -> ()
`seq` Strategy h
strat8 h
x8 () -> () -> ()
`seq` Strategy i
strat9 i
x9