-- Hoogle documentation, generated by Haddock
-- See Hoogle, http://www.haskell.org/hoogle/


-- | Deep evaluation of data structures
--   
--   This package provides methods for fully evaluating data structures
--   ("deep evaluation"). Deep evaluation is often used for adding
--   strictness to a program, e.g. in order to force pending exceptions,
--   remove space leaks, or force lazy I/O to happen. It is also useful in
--   parallel programs, to ensure pending work does not migrate to the
--   wrong thread.
--   
--   The primary use of this package is via the <a>deepseq</a> function, a
--   "deep" version of <a>seq</a>. It is implemented on top of an
--   <a>NFData</a> typeclass ("Normal Form Data", data structures with no
--   unevaluated components) which defines strategies for fully evaluating
--   different data types.
@package deepseq
@version 1.2.0.1


-- | This module provides an overloaded function, <a>deepseq</a>, for fully
--   evaluating data structures (that is, evaluating to "Normal Form").
--   
--   A typical use is to prevent resource leaks in lazy IO programs, by
--   forcing all characters from a file to be read. For example:
--   
--   <pre>
--   import System.IO
--   import Control.DeepSeq
--   
--   main = do
--       h &lt;- openFile "f" ReadMode
--       s &lt;- hGetContents h
--       s `deepseq` hClose h
--       return s
--   </pre>
--   
--   <a>deepseq</a> differs from <a>seq</a> as it traverses data structures
--   deeply, for example, <a>seq</a> will evaluate only to the first
--   constructor in the list:
--   
--   <pre>
--   &gt; [1,2,undefined] `seq` 3
--   3
--   </pre>
--   
--   While <a>deepseq</a> will force evaluation of all the list elements:
--   
--   <pre>
--   &gt; [1,2,undefined] `deepseq` 3
--   *** Exception: Prelude.undefined
--   </pre>
--   
--   Another common use is to ensure any exceptions hidden within lazy
--   fields of a data structure do not leak outside the scope of the
--   exception handler, or to force evaluation of a data structure in one
--   thread, before passing to another thread (preventing work moving to
--   the wrong threads).
module Control.DeepSeq

-- | <a>deepseq</a>: fully evaluates the first argument, before returning
--   the second.
--   
--   The name <a>deepseq</a> is used to illustrate the relationship to
--   <a>seq</a>: where <a>seq</a> is shallow in the sense that it only
--   evaluates the top level of its argument, <a>deepseq</a> traverses the
--   entire data structure evaluating it completely.
--   
--   <a>deepseq</a> can be useful for forcing pending exceptions,
--   eradicating space leaks, or forcing lazy I/O to happen. It is also
--   useful in conjunction with parallel Strategies (see the
--   <tt>parallel</tt> package).
--   
--   There is no guarantee about the ordering of evaluation. The
--   implementation may evaluate the components of the structure in any
--   order or in parallel. To impose an actual order on evaluation, use
--   <tt>pseq</tt> from <a>Control.Parallel</a> in the <tt>parallel</tt>
--   package.
deepseq :: NFData a => a -> b -> b

-- | the deep analogue of <a>$!</a>. In the expression <tt>f $!! x</tt>,
--   <tt>x</tt> is fully evaluated before the function <tt>f</tt> is
--   applied to it.
($!!) :: NFData a => (a -> b) -> a -> b

-- | a variant of <a>deepseq</a> that is useful in some circumstances:
--   
--   <pre>
--   force x = x `deepseq` x
--   </pre>
--   
--   <tt>force x</tt> fully evaluates <tt>x</tt>, and then returns it. Note
--   that <tt>force x</tt> only performs evaluation when the value of
--   <tt>force x</tt> itself is demanded, so essentially it turns shallow
--   evaluation into deep evaluation.
force :: NFData a => a -> a

-- | A class of types that can be fully evaluated.
class NFData a
rnf :: NFData a => a -> ()
instance (NFData a1, NFData a2, NFData a3, NFData a4, NFData a5, NFData a6, NFData a7, NFData a8, NFData a9) => NFData (a1, a2, a3, a4, a5, a6, a7, a8, a9)
instance (NFData a1, NFData a2, NFData a3, NFData a4, NFData a5, NFData a6, NFData a7, NFData a8) => NFData (a1, a2, a3, a4, a5, a6, a7, a8)
instance (NFData a1, NFData a2, NFData a3, NFData a4, NFData a5, NFData a6, NFData a7) => NFData (a1, a2, a3, a4, a5, a6, a7)
instance (NFData a1, NFData a2, NFData a3, NFData a4, NFData a5, NFData a6) => NFData (a1, a2, a3, a4, a5, a6)
instance (NFData a1, NFData a2, NFData a3, NFData a4, NFData a5) => NFData (a1, a2, a3, a4, a5)
instance (NFData a, NFData b, NFData c, NFData d) => NFData (a, b, c, d)
instance (NFData a, NFData b, NFData c) => NFData (a, b, c)
instance (NFData a, NFData b) => NFData (a, b)
instance (Ix a, NFData a, NFData b) => NFData (Array a b)
instance NFData a => NFData [a]
instance (NFData a, NFData b) => NFData (Either a b)
instance NFData a => NFData (Maybe a)
instance (RealFloat a, NFData a) => NFData (Complex a)
instance (Integral a, NFData a) => NFData (Ratio a)
instance NFData Word64
instance NFData Word32
instance NFData Word16
instance NFData Word8
instance NFData Int64
instance NFData Int32
instance NFData Int16
instance NFData Int8
instance NFData ()
instance NFData Bool
instance NFData Char
instance NFData Double
instance NFData Float
instance NFData Integer
instance NFData Word
instance NFData Int