    -- ------------------------------------------------------------

    {- |
       Module     : Control.Arrow.ArrowNF
       Copyright  : Copyright (C) 2011 Uwe Schmidt
       License    : MIT

       Maintainer : Uwe Schmidt (uwe\@fh-wedel.de)
       Stability  : experimental
       Portability: non-portable

       Arrows for evaluation of normal form results

    -}

    -- ------------------------------------------------------------

    module Control.Arrow.ArrowNF
    where

    import           Control.Arrow
    import           Control.Arrow.ArrowList

    import           Control.DeepSeq
    import           Control.FlatSeq

    -- |
    -- complete evaluation of an arrow result using 'Control.DeepSeq'
    --
    -- this is sometimes useful for preventing space leaks, especially after reading
    -- and validation of a document, all DTD stuff is not longer in use and can be
    -- recycled by the GC.

    strictA :: (Arrow a, NFData b) => a b b
    strictA = arr $ \ x -> deepseq x x

    class (Arrow a) => ArrowNF a where
        rnfA                        :: (NFData c) => a b c -> a b c
        rnfA f                      = f >>^ (\ x -> deepseq x x)
        {-# INLINE rnfA #-}

    -- |
    -- partial evaluation of an arrow result using 'Control.FlatSeq'
    --
    -- There are tow arrows with force the partial evaluation. By convention
    -- the 2. should be less lazy than the 1.
    --
    -- These arrows are sometimes useful for preventing space leaks, especially when parsing
    -- complex data structures. In many cases the evaluated AST is more space efficient
    -- than the unevaluaded with a lot of closures.

    class (Arrow a, ArrowList a) => ArrowWNF a where
        rwnfA                       :: (WNFData c) => a b c -> a b c
        rwnfA f                     = f >>. \ x -> rlnf rwnf x `seq` x
        {-# INLINE rwnfA #-}

        rwnf2A                      :: (WNFData c) => a b c -> a b c
        rwnf2A f                    = f >>. \ x -> rlnf rwnf2 x `seq` x
        {-# INLINE rwnf2A #-}

    -- ------------------------------------------------------------