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


-- | Provides Template Haskell deriver for NFData instances
--   
--   Provides a Template Haskell based mechanism for deriving NFData
--   instances for custom data types. See documentation in
--   <a>Control.DeepSeq.TH</a> for more information.
@package deepseq-th
@version 0.0.0.0

module Control.DeepSeq.TH

-- | Derive <a>NFData</a> instance for simple <tt>Data</tt>-declarations
--   
--   Example usage for deriving <a>NFData</a> instance for the type
--   <tt>TypeName</tt>:
--   
--   <pre>
--   $(deriveNFData ''TypeName)
--   </pre>
--   
--   The derivation tries to avoid evaluation of strict fields whose types
--   have the WHNF=NF property (see also <a>whnfIsNf</a>). For instance,
--   consider the following type <tt>Foo</tt>:
--   
--   <pre>
--   data Foo a = Foo1
--              | Foo2 !Int !String
--              | Foo3 (Foo a)
--              | Foo4 { fX :: Int, fY :: Char }
--              | Foo a :--: !Bool
--   </pre>
--   
--   By invoking <tt>$(deriveNFData ''Foo)</tt> the generated <a>NFData</a>
--   instance will be equivalent to:
--   
--   <pre>
--   instance NFData a =&gt; NFData (Foo a) where
--       rnf Foo1       = ()
--       rnf (Foo2 _ x) = x `deepseq` ()
--       rnf (Foo3 x)   = x `deepseq` ()
--       rnf (Foo4 x y) = x `deepseq` y `deepseq` ()
--       rnf (x :--: _) = x `deepseq` ()
--   </pre>
--   
--   Known issues/limitations:
--   
--   <ul>
--   <li><tt>TypeName</tt> must be a proper <tt>data</tt> typename (use the
--   <tt>GeneralizedNewtypeDeriving</tt> extension for <tt>newtype</tt>
--   names)</li>
--   <li>Does not support existential types yet (i.e. use of the
--   <tt>forall</tt> keyword)</li>
--   <li>Does not always detect phantom type variables (e.g. for <tt>data
--   Foo a = Foo0 | Foo1 (Foo a)</tt>) which causes those to require
--   <a>NFData</a> instances.</li>
--   </ul>
deriveNFData :: Name -> Q [Dec]

-- | Plural version of <a>deriveNFData</a>
--   
--   Convenience wrapper for <a>deriveNFData</a> which allows to derive
--   multiple <a>NFData</a> instances for a list of <tt>TypeName</tt>s,
--   e.g.:
--   
--   <pre>
--   $(deriveNFData [''TypeName1, ''TypeName2, ''TypeName3])
--   </pre>
deriveNFDatas :: [Name] -> Q [Dec]

-- | Try to infer whether type has the property that WHNF=NF for its
--   values.
--   
--   A result of <tt>Nothing</tt> means it is not known whether the
--   property holds for the given type. <tt>Just True</tt> means that the
--   property holds.
--   
--   This function has currently a very limited knowledge and returns
--   <tt>Nothing</tt> most of the time except for some primitive types.
whnfIsNf :: Type -> Maybe Bool