-- Hoogle documentation, generated by Haddock
-- See Hoogle, http://www.haskell.org/hoogle/
-- | A typeclass to determine if a given value is null.
--
-- A typeclass to determine if a given foldable type (or other) is empty
-- ~ null ~ invalid. The definition is intentionally vague, to cover
-- types from Either to Text and Sets.
@package IsNull
@version 0.4.0.0
-- | A typeclass to determine if a given value is null.
--
-- Strongly inspired by mono-traversable but with a simpler goal:
-- supporting IsNull and nested IsNull operations.
--
-- While the isNull function is equivalent to (==)
-- mempty for most of the instances, not all
-- Foldables are monoids, and not all monoids
-- mempty means null:
--
--
-- - Either is an example of a Foldable which
-- is not a Monoid, but where it makes sense to
-- consider a Left as an Null value. While this
-- is not strictly true, the Left option does carries a
-- value, we take the more liberal approach: Empty ~ Null ~ Invalid
-- Value. If you need proper type reasoning, you should not be using this
-- package, just regular pattern matching instead.
-- - Product Monoid instance is
-- 1. Hardly qualifies as an Empty or Null
-- value. For this reason no default implementation is provided for the
-- Monoid class. It's up to you to use (==)
-- mempty instead.
--
--
-- This class is suitable for use with
-- GeneralizedNewtypeDeriving, thanks to the precious help of
-- Ivan Miljenovic.
--
-- Bugs, suggestions and comments are most welcomed!
--
-- https://github.com/jcristovao/IsNull
module Data.IsNull
class IsNull a
isNull :: IsNull a => a -> Bool
-- | the logical negation of isNull
notNull :: IsNull a => a -> Bool
-- | Nested isNull
--
--
-- >>> isNullN (Just "abc")
-- False
--
--
--
-- >>> isNullN (Just "")
-- True
--
--
--
-- >>> isNullN (Nothing :: Maybe String)
-- True
--
isNullN :: (IsNull a, Foldable f) => f a -> Bool
-- | Nested isNotNull
notNullN :: (IsNull a, Foldable f) => f a -> Bool
-- | Monadic isNull
--
--
-- >>> isNullM [""]
-- [True]
--
isNullM :: (IsNull a, Functor m) => m a -> m Bool
-- | Monadic Nested isNull
isNullNM :: (IsNull a, Functor m, Foldable f) => m (f a) -> m Bool
(<\>) :: IsNull a => a -> a -> a
instance [overlap ok] Foldable f => IsNull (f a)
instance [overlap ok] IsNull IntSet
instance [overlap ok] IsNull ByteString
instance [overlap ok] IsNull ByteString
instance [overlap ok] IsNull Text
instance [overlap ok] IsNull Text