Add the delete function to Vector.hs.

diff --git a/src/Linear/Vector.hs b/src/Linear/Vector.hs
index aba9e5fb2d28d3d5ae43665ca95353f3cc8b6fd5..a7885e4aea628b91fdb205b232602082e52093e5 100644 (file)
--- a/src/Linear/Vector.hs
+++ b/src/Linear/Vector.hs
@@ -14,8 +14,10 @@ import Data.Vector.Fixed (
   N2,
   N3,
   N4,
+  S,
   Vector(..),
   construct,
+  fromList,
   inspect,
   toList,
   )
@@ -31,25 +33,25 @@ import qualified Data.Vector.Fixed as V (
 -- constructors, so you can pattern match out the individual
 -- components.
 
-data D1 a = D1 a
+data D1 a = D1 a deriving (Show, Eq)
 type instance Dim D1 = N1
 instance Vector D1 a where
   inspect (D1 x) (Fun f) = f x
   construct = Fun D1
 
-data D2 a = D2 a a
+data D2 a = D2 a a deriving (Show, Eq)
 type instance Dim D2 = N2
 instance Vector D2 a where
   inspect (D2 x y) (Fun f) = f x y
   construct = Fun D2
 
-data D3 a = D3 a a a
+data D3 a = D3 a a a deriving (Show, Eq)
 type instance Dim D3 = N3
 instance Vector D3 a where
   inspect (D3 x y z) (Fun f) = f x y z
   construct = Fun D3
 
-data D4 a = D4 a a a a
+data D4 a = D4 a a a a deriving (Show, Eq)
 type instance Dim D4 = N4
 instance Vector D4 a where
   inspect (D4 w x y z) (Fun f) = f w x y z
@@ -81,3 +83,19 @@ instance Vector D4 a where
 (!?) v1 idx
   | idx < 0 || idx >= V.length v1 = Nothing
   | otherwise                     = Just $ v1 ! idx
+
+
+-- | Remove an element of the given vector.
+--
+--   Examples:
+--
+--   >>> let b = D3 1 2 3
+--   >>> delete b 1 :: D2 Int
+--   D2 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