-- Hoogle documentation, generated by Haddock -- See Hoogle, http://www.haskell.org/hoogle/ -- | Generates Matchable instances using TemplateHaskell -- -- This package provides TemplateHaskell function to generate instances -- of Matchable and Bimatchable type classes, which are -- from "matchable" package. @package matchable-th @version 0.2.1 module Data.Matchable.TH -- | Derive multiple instances of Matchable, Bimatchable, or -- their superclasses, each written in StandaloneDeriving -- syntax. -- -- Passing declarations other than standalone deriving instances is an -- error. Also, passing any instances other than Matchable, -- Bimatchable or their superclasses is an error. Explicitly, it -- accepts standalone deriving declarations of the following types: -- --

-- -- Passing an Eq or Functor instance declarations does not -- cause a compilation error and generates the same standalone deriving -- declaration passed in, but also causes a warning telling you -- that you can use stock deriving for them. -- --

Example

-- --

--   {-# LANGUAGE DeriveFunctor #-}
--   {-# LANGUAGE StandaloneDeriving #-}
--   [-# LANGUAGE TemplateHaskell #-}
--   data Foo a b = Foo a b (Either a b)
--      deriving (Show, Eq, Functor)
--   
--

-- -- To use deriveInstances for Foo, write as below: -- --

--   deriveInstances [d|
--     deriving instance Eq a => Eq1 (Foo a)
--     deriving instance Eq a => Matchable (Foo a)
--     deriving instance Eq2 Foo
--     deriving instance Bifunctor Foo
--     deriving instance Bimatchable Foo
--     |]
--   
--

deriveInstances :: Q [Dec] -> Q [Dec] -- | Build an instance of Matchable for a data type. -- -- Note that deriveMatchable generates the Matchable -- instance only. Because Matchable requires Functor and -- Eq1 (and Eq transitively) as its superclasses, to -- actually use the generated instance, it's necessary to provide them -- too. -- -- Use deriveInstances to generate both Matchable and -- Eq1 instances at once. -- --

Example

-- --

--   data Exp a = Plus a a | Times a a
--   deriveMatchable ''Exp
--

-- -- will generate the following instance. -- --

--   instance Matchable Exp where
--     zipMatchWith f (Plus  l1 l2) (Plus  r1 r2) = pure Plus  * f l1 r1 * f l2 r2
--     zipMatchWith f (Times l1 l2) (Times r1 r2) = pure Times * f l1 r1 * f l2 r2
--     zipMatchWith _ _ _ = Nothing
--

deriveMatchable :: Name -> Q [Dec] -- | Build an instance of Bimatchable for a data type. -- -- Note that deriveBimatchable generates the Bimatchable -- instance only. Because Bimatchable requires Bifunctor -- and Eq2 (and Functor, Eq, Eq1 -- transitively) as its superclasses, to actually use the generated -- instance, it's necessary to provide them too. -- -- Use deriveInstances to generate all of these instances at once. -- --

Example

-- --

--   data Sum a b = InL a | InR b
--   deriveBimatchable ''Sum
--

-- -- will create -- --

--   instance Bimatchable Sum where
--     bizipMatchWith f _ (InL l1) (InL r1) = pure InL $ f l1 r1
--     bizipMatchWith _ g (InR l1) (InR r1) = pure InR $ g l1 r1
--

deriveBimatchable :: Name -> Q [Dec] -- | Generates an expression which behaves like zipMatchWith for the -- given data type. makeZipMatchWith :: Name -> ExpQ -- | Generates an expression which behaves like bizipMatchWith for -- the given data type. makeBizipMatchWith :: Name -> ExpQ -- | Generates an expression which behaves like liftEq for the given -- data type. makeLiftEq :: Name -> Q Exp -- | Generates an expression which behaves like liftEq2 for the -- given data type. makeLiftEq2 :: Name -> Q Exp