src/Linear/Vector.hs

   1 {-# LANGUAGE FlexibleContexts #-}
   2 {-# LANGUAGE FlexibleInstances #-}
   3 {-# LANGUAGE MultiParamTypeClasses #-}
   4 {-# LANGUAGE NoImplicitPrelude #-}
   5 {-# LANGUAGE NoMonomorphismRestriction #-}
   6 {-# LANGUAGE ScopedTypeVariables #-}
   7 {-# LANGUAGE TypeFamilies #-}
   8
   9 module Linear.Vector (
  10   module Data.Vector.Fixed.Boxed,
  11   Vec0,
  12   Vec1,
  13   (!?),
  14   delete,
  15   element_sum )
  16 where
  17
  18 import qualified Algebra.Additive as Additive ( C )
  19 import qualified Algebra.Ring as Ring ( C )
  20 import Data.Vector.Fixed (
  21   Dim,
  22   N1,
  23   S,
  24   Vector(..),
  25   Z,
  26   fromList,
  27   toList )
  28 import Data.Vector.Fixed (
  29   (!),
  30   foldl,
  31   length )
  32 import Data.Vector.Fixed.Boxed (
  33   Vec,
  34   Vec2,
  35   Vec3,
  36   Vec4,
  37   Vec5 )
  38 import NumericPrelude hiding ( abs, length, foldl )
  39
  40 type Vec0 = Vec Z
  41 type Vec1 = Vec N1
  42
  43
  44
  45 -- | Safe indexing.
  46 --
  47 --   Examples:
  48 --
  49 --   >>> import Data.Vector.Fixed (mk3)
  50 --   >>> let v1 = mk3 1 2 3 :: Vec3 Int
  51 --   >>> v1 !? 2
  52 --   Just 3
  53 --   >>> v1 !? 3
  54 --   Nothing
  55 --
  56 (!?) :: (Vector v a) => v a -> Int -> Maybe a
  57 (!?) v1 idx
  58   | idx < 0 || idx >= length v1 = Nothing
  59   | otherwise                   = Just $ v1 ! idx
  60
  61
  62 -- | Remove an element of the given vector.
  63 --
  64 --   Examples:
  65 --
  66 --   >>> import Data.Vector.Fixed (mk3)
  67 --   >>> let b = mk3 1 2 3 :: Vec3 Int
  68 --   >>> delete b 1 :: Vec2 Int
  69 --   fromList [1,3]
  70 --
  71 delete :: (Vector v a,
  72            Vector w a,
  73            Dim v ~ S (Dim w))
  74        => v a
  75        -> Int
  76        -> w a
  77 delete v1 idx =
  78   fromList (lhalf ++ rhalf')
  79   where
  80     (lhalf, rhalf) = splitAt idx (toList v1)
  81     rhalf' = tail rhalf
  82
  83
  84 -- | We provide our own sum because sum relies on a Num instance
  85 --   from the Prelude that we don't have.
  86 --
  87 --   Examples:
  88 --
  89 --   >>> import Data.Vector.Fixed (mk3)
  90 --   >>> let b = mk3 1 2 3 :: Vec3 Int
  91 --   >>> element_sum b
  92 --   6
  93 --
  94 element_sum :: (Additive.C a, Ring.C a, Vector v a) => v a -> a
  95 element_sum = foldl (+) (fromInteger 0)