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


-- | A type class for empty containers
--   
--   HasEmpty f has a member empty of type forall a. f a
@package Empty
@version 0.1.0.0

module Control.Empty

-- | The class of type of <tt>* -&gt; *</tt> which may be empty. There is
--   only one law for HasEmpty and its enforced by the type. The law is
--   that there exists a value in type f for which a is fully generic. This
--   alone is often enough to uniquely determine the value for a given,
--   data type.
--   
--   Additional laws for HasEmpty work backwards, <tt>empty</tt> has a
--   relationships with other classes. So if <tt>f</tt> is a member of one
--   of these classes, the following should hold.
--   
--   <ul>
--   <li><i><i>Functor identity</i></i> <pre>g &lt;$&gt; empty =
--   empty</pre></li>
--   <li><i><i>Applicative annililation left</i></i> <pre>x &lt;*&gt; empty
--   = empty</pre></li>
--   <li><i><i>Applicative annililation right</i></i> <pre>empty &lt;*&gt;
--   x = empty</pre></li>
--   <li><i><i>Monad identity</i></i> <pre>empty &gt;&gt;= f =
--   empty</pre></li>
--   <li><i><i>Alternative empty</i></i> <pre>empty =
--   Alternative.empty</pre></li>
--   <li><i><i>MonadPlus mzero</i></i> <pre>empty = mzero</pre></li>
--   <li><i><i>Foldable identity</i></i> <pre>foldr f x empty =
--   empty</pre></li>
--   </ul>
class HasEmpty f where empty = empty
empty :: forall a. HasEmpty f => f a
empty :: (HasEmpty f, Alternative f) => f a
coerce :: HasEmpty f => a -> f b
isEmpty :: (HasEmpty f, Eq (f a)) => f a -> Bool
instance Control.Empty.HasEmpty GHC.Base.Maybe
instance Control.Empty.HasEmpty []
instance Control.Empty.HasEmpty GHC.Types.IO
instance Control.Empty.HasEmpty GHC.Conc.Sync.STM
instance Control.Empty.HasEmpty Data.Proxy.Proxy
instance Control.Empty.HasEmpty Data.Semigroup.Option
instance Control.Empty.HasEmpty Text.ParserCombinators.ReadP.ReadP
instance Control.Empty.HasEmpty Text.ParserCombinators.ReadPrec.ReadPrec
instance (GHC.Base.Alternative f, GHC.Base.Alternative g) => Control.Empty.HasEmpty (Data.Functor.Product.Product f g)
instance (GHC.Base.Alternative f, GHC.Base.Applicative g) => Control.Empty.HasEmpty (Data.Functor.Compose.Compose f g)
instance Control.Empty.HasEmpty Data.IntMap.Base.IntMap
instance Control.Empty.HasEmpty (Data.Map.Base.Map k)
instance Control.Empty.HasEmpty Data.Sequence.Seq
instance Control.Empty.HasEmpty Data.Set.Base.Set