{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TypeFamilies #-}

module Linear.Vector
where

import Data.Vector.Fixed (
  Dim,
  N1,
  N4,
  N5,
  S,
  Vector(..),
  fromList,
  toList,
  )
import qualified Data.Vector.Fixed as V (
  (!),
  length,
  )
import Data.Vector.Fixed.Boxed

type Vec1 = Vec N1
type Vec4 = Vec N4
type Vec5 = Vec N5



-- | Safe indexing.
--
--   Examples:
--
--   >>> import Data.Vector.Fixed (mk3)
--   >>> let v1 = mk3 1 2 3 :: Vec3 Int
--   >>> v1 !? 2
--   Just 3
--   >>> v1 !? 3
--   Nothing
--
(!?) :: (Vector v a) => v a -> Int -> Maybe a
(!?) v1 idx
  | idx < 0 || idx >= V.length v1 = Nothing
  | otherwise                     = Just $ v1 V.! idx


-- | Remove an element of the given vector.
--
--   Examples:
--
--   >>> import Data.Vector.Fixed (mk3)
--   >>> let b = mk3 1 2 3 :: Vec3 Int
--   >>> delete b 1 :: Vec2 Int
--   fromList [1,3]
--
delete :: (Vector v a,
           Vector w a,
           Dim v ~ S (Dim w))
       => v a
       -> Int
       -> w a
delete v1 idx =
  fromList (lhalf ++ rhalf')
  where
    (lhalf, rhalf) = splitAt idx (toList v1)
    rhalf' = tail rhalf