{-# LANGUAGE CPP #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE Safe #-}
-----------------------------------------------------------------------------

-- |

-- Copyright   :  (C) 2011-2015 Edward Kmett

-- License     :  BSD-style (see the file LICENSE)

--

-- Maintainer  :  Edward Kmett <ekmett@gmail.com>

-- Stability   :  provisional

-- Portability :  portable

--

----------------------------------------------------------------------------

module Data.Semigroup.Traversable
  ( Traversable1(..)
  -- * Defining Traversable1 instances

  -- $traversable1instances

  , traverse1Maybe
  , gtraverse1
  , gsequence1
  -- * Default superclass instance helpers

  , foldMap1Default
  ) where

import Control.Applicative
#if !(MIN_VERSION_base(4,11,0))
import Data.Semigroup
#endif
import Data.Semigroup.Traversable.Class
import Data.Functor.Bind.Class
import GHC.Generics

-- | Default implementation of 'foldMap1' given an implementation of 'Traversable1'.

foldMap1Default :: (Traversable1 f, Semigroup m) => (a -> m) -> f a -> m
foldMap1Default :: forall (f :: * -> *) m a.
(Traversable1 f, Semigroup m) =>
(a -> m) -> f a -> m
foldMap1Default a -> m
f = forall {k} a (b :: k). Const a b -> a
getConst forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall (t :: * -> *) (f :: * -> *) a b.
(Traversable1 t, Apply f) =>
(a -> f b) -> t a -> f (t b)
traverse1 (forall {k} a (b :: k). a -> Const a b
Const forall b c a. (b -> c) -> (a -> b) -> a -> c
. a -> m
f)

-- | Generic 'traverse1'. Caveats:

--

--   1. Will not compile if @t@ is an empty constructor.

--   2. Will not compile if @t@ has some fields that don't mention @a@, for exmaple @data Bar a = MkBar a Int@

--

-- @since 5.3.8

gtraverse1 ::
  (Traversable1 (Rep1 t), Apply f, Generic1 t) =>
  (a -> f b) ->
  t a ->
  f (t b)
gtraverse1 :: forall (t :: * -> *) (f :: * -> *) a b.
(Traversable1 (Rep1 t), Apply f, Generic1 t) =>
(a -> f b) -> t a -> f (t b)
gtraverse1 a -> f b
f t a
x = forall k (f :: k -> *) (a :: k). Generic1 f => Rep1 f a -> f a
to1 forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> forall (t :: * -> *) (f :: * -> *) a b.
(Traversable1 t, Apply f) =>
(a -> f b) -> t a -> f (t b)
traverse1 a -> f b
f (forall k (f :: k -> *) (a :: k). Generic1 f => f a -> Rep1 f a
from1 t a
x)

-- | Generic 'sequence1'. Caveats are the same for 'gtraverse1'.

--

-- @since 5.3.8

gsequence1 ::
  (Traversable1 (Rep1 t), Apply f, Generic1 t) =>
  t (f b) ->
  f (t b)
gsequence1 :: forall (t :: * -> *) (f :: * -> *) b.
(Traversable1 (Rep1 t), Apply f, Generic1 t) =>
t (f b) -> f (t b)
gsequence1 = forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
fmap forall k (f :: k -> *) (a :: k). Generic1 f => Rep1 f a -> f a
to1 forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall (t :: * -> *) (f :: * -> *) b.
(Traversable1 t, Apply f) =>
t (f b) -> f (t b)
sequence1 forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall k (f :: k -> *) (a :: k). Generic1 f => f a -> Rep1 f a
from1

-- $traversable1instances

-- Defining 'Traversable1' instances for types with both 'Traversable1' and 'Traversable'

-- substructures can be done with 'traverse1Maybe', '(<*.>)', and '(<.*>)'.

--

-- > data Foo a = Foo (Maybe a) (Maybe a) a [a]

-- >   deriving (Functor, Traversable, Foldable)

-- > instance Traversable1 Foo where

-- >   traverse1 f (Foo ma ma' a as) = Foo <$> traverseMaybe ma <*> traverseMaybe ma' <*.> f a <.*> traverseMaybe as

-- > instance Foldable1 Foo where

-- >   foldMap1 = foldMap1Default