src/Linear/Vector.hs

   1 {-# LANGUAGE FlexibleContexts #-}
   2 {-# LANGUAGE FlexibleInstances #-}
   3 {-# LANGUAGE MultiParamTypeClasses #-}
   4 {-# LANGUAGE ScopedTypeVariables #-}
   5 {-# LANGUAGE TypeFamilies #-}
   6
   7 module Linear.Vector
   8 where
   9
  10 import Data.Vector.Fixed (
  11   Dim,
  12   Fun(..),
  13   N1,
  14   N2,
  15   N3,
  16   N4,
  17   Vector(..),
  18   construct,
  19   inspect,
  20   toList,
  21   )
  22 import qualified Data.Vector.Fixed as V (
  23   length,
  24   )
  25
  26
  27 -- * Low-dimension vector wrappers.
  28 --
  29 -- These wrappers are instances of 'Vector', so they inherit all of
  30 -- the userful instances defined above. But, they use fixed
  31 -- constructors, so you can pattern match out the individual
  32 -- components.
  33
  34 data D1 a = D1 a
  35 type instance Dim D1 = N1
  36 instance Vector D1 a where
  37   inspect (D1 x) (Fun f) = f x
  38   construct = Fun D1
  39
  40 data D2 a = D2 a a
  41 type instance Dim D2 = N2
  42 instance Vector D2 a where
  43   inspect (D2 x y) (Fun f) = f x y
  44   construct = Fun D2
  45
  46 data D3 a = D3 a a a
  47 type instance Dim D3 = N3
  48 instance Vector D3 a where
  49   inspect (D3 x y z) (Fun f) = f x y z
  50   construct = Fun D3
  51
  52 data D4 a = D4 a a a a
  53 type instance Dim D4 = N4
  54 instance Vector D4 a where
  55   inspect (D4 w x y z) (Fun f) = f w x y z
  56   construct = Fun D4
  57
  58
  59 -- | Unsafe indexing.
  60 --
  61 --   Examples:
  62 --
  63 --   >>> let v1 = D2 1 2
  64 --   >>> v1 ! 1
  65 --   2
  66 --
  67 (!) :: (Vector v a) => v a -> Int -> a
  68 (!) v1 idx = (toList v1) !! idx
  69
  70 -- | Safe indexing.
  71 --
  72 --   Examples:
  73 --
  74 --   >>> let v1 = D3 1 2 3
  75 --   >>> v1 !? 2
  76 --   Just 3
  77 --   >>> v1 !? 3
  78 --   Nothing
  79 --
  80 (!?) :: (Vector v a) => v a -> Int -> Maybe a
  81 (!?) v1 idx
  82   | idx < 0 || idx >= V.length v1 = Nothing
  83   | otherwise                     = Just $ v1 ! idx