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