Indexed.hs

{-# LANGUAGE FlexibleInstances      #-}
{-# LANGUAGE FunctionalDependencies #-}
-----------------------------------------------------------------------------
-- | Module     :  Data.Align.Indexed
--
-- 'These'-based zipping and unzipping of indexed functors.
--
-- @since 0.7.6
module Data.Align.Indexed (
    AlignWithIndex (..),
    ) where

import Control.Lens          (FunctorWithIndex (imap))
import Data.Vector.Instances ()

import Data.Align
import Data.These

-- Instances
import Control.Applicative (ZipList)
import Data.Hashable       (Hashable)
import Data.HashMap.Strict (HashMap)
import Data.IntMap         (IntMap)
import Data.Map            (Map)
import Data.Sequence       (Seq)
import Data.Vector         (Vector)

-- | Keyed version of 'Align'.
--
-- @since 0.7.6
class (FunctorWithIndex i f, Semialign f) => AlignWithIndex i f | f -> i where
    -- | Analogous to @'alignWith'@, but also provides an index.
    ialign :: (i -> These a b -> c) -> f a -> f b -> f c
    ialign f a b = imap f (align a b)

instance AlignWithIndex () Maybe
instance AlignWithIndex Int []
instance AlignWithIndex Int ZipList
instance AlignWithIndex Int Seq
instance AlignWithIndex Int IntMap
instance Ord k => AlignWithIndex k (Map k)
instance (Eq k, Hashable k) => AlignWithIndex k (HashMap k)
instance AlignWithIndex Int Vector