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


-- | A class for types with a default value.
--   
--   An alternative to <a>data-default</a> package, that provides a lot of
--   additional instances for <tt>Default</tt> type class.
--   
--   <tt>Default</tt> type class provides a default value (<tt>def</tt>) of
--   a type. In case when a particluar type has an instance for
--   <tt>Monoid</tt>, then the default value should be <tt>mempty</tt>,
--   otherwise it can cause a great deal of confusion.
--   
--   One must understand, that <tt>Default</tt> type class, has no axioms
--   associated with it. Its purpose is to minimize:
--   
--   <ul>
--   <li>Number of imports.</li>
--   <li>Number of introduced definitions that are part of an API.</li>
--   <li>Complexity of building more complicated "default values" out of
--   simpler "default values".</li>
--   <li>Cognitive overhead. (Reduction of cognitive overhead is partially
--   a consequence of reducing above issues.)</li>
--   </ul>
--   
--   As one may notice, most of the listed problems, that <tt>Default</tt>
--   type class tries to solve, to various degrees of success, are for
--   human benefit, and not theoretically founded. Because of this, please
--   always try hard to define sensible instances of <tt>Default</tt>. Most
--   importantly, document what <tt>def</tt> means for particular type, and
--   always check that <tt>def</tt> is sensible, by testing it on a real
--   world sample of human beings, one is not a big enough sample.
--   
--   That said, using <tt>Default</tt> may not always be a good idea. If it
--   breaks people's mental model, or theoretical models with real axioms,
--   then just don't use it.
@package data-default-extra
@version 0.0.1


-- | Create <a>Default</a> instances using GHC Generics. For more
--   information see:
--   
--   <ul>
--   <li><a>GHC User's Guide</a></li>
--   <li><a>HaskellWiki: GHC.Generics</a></li>
--   </ul>
module Data.Default.Generic

-- | Derive implementation of <a>def</a> by using GHC Generics.
genericDef :: (Generic a, GDefault (Rep a)) => a

-- | Simple derivation of <a>def</a> definition that handles only product
--   types, but not sum types. In case of sum types it is better to provide
--   hand written instances for <a>Default</a>.
class GDefault f
gdef :: GDefault f => f a
instance Data.Default.Generic.GDefault GHC.Generics.U1
instance Data.Default.Class.Default a => Data.Default.Generic.GDefault (GHC.Generics.K1 i a)
instance Data.Default.Generic.GDefault a => Data.Default.Generic.GDefault (GHC.Generics.M1 i c a)
instance (Data.Default.Generic.GDefault a, Data.Default.Generic.GDefault b) => Data.Default.Generic.GDefault (a GHC.Generics.:*: b)


-- | A class for types with a default value.
module Data.Default

-- | A class for types with a default value.
class Default a

-- | The default value for this type.
def :: Default a => a

-- | The default value for type <tt>a</tt>.
defOf :: Default a => proxy a -> a