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diff --git a/lib/LinearAlgebra/Interface.hs b/lib/LinearAlgebra/Interface.hs
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+{-# OPTIONS_GHC -fglasgow-exts #-}
+-----------------------------------------------------------------------------
+{- |
+Module      :  LinearAlgebra.Interface
+Copyright   :  (c) Alberto Ruiz 2006
+License     :  GPL-style
+
+Maintainer  :  Alberto Ruiz (aruiz at um dot es)
+Stability   :  provisional
+Portability :  portable
+
+Operators for frequent operations.
+
+-}
+-----------------------------------------------------------------------------
+
+module LinearAlgebra.Interface(
+    (<>),(<.>),
+    (.*),(*/),
+    (<|>),(<->),
+) where
+
+import LinearAlgebra.Linear
+import Data.Packed.Vector
+import Data.Packed.Matrix
+
+class Mul a b c | a b -> c where
+ infixl 7 <>
+ -- | matrix product
+ (<>) :: Field t => a t -> b t -> c t
+
+instance Mul Matrix Matrix Matrix where
+    (<>) = multiply
+
+instance Mul Matrix Vector Vector where
+    (<>) m v = flatten $ m <> (asColumn v)
+
+instance Mul Vector Matrix Vector where
+    (<>) v m = flatten $ (asRow v) <> m
+
+---------------------------------------------------
+
+-- | @u \<.\> v = dot u v@
+(<.>) :: (Field t) => Vector t -> Vector t -> t
+infixl 7 <.>
+(<.>) = dot
+
+----------------------------------------------------
+
+-- | @x .* a = scale (recip x) v@
+(.*) :: (Linear c a) => a -> c a -> c a
+infixl 7 .*
+a .* x = scale a x
+
+----------------------------------------------------
+
+-- | @a *\/ x = scale (recip x) a@
+(*/) :: (Linear c a) => c a -> a -> c a
+infixl 7 */
+v */ x = scale (recip x) v
+
+------------------------------------------------
+
+class Joinable a b where
+    joinH :: Field t => a t -> b t -> Matrix t
+    joinV :: Field t => a t -> b t -> Matrix t
+
+instance Joinable Matrix Matrix where
+    joinH m1 m2 = fromBlocks [[m1,m2]]
+    joinV m1 m2 = fromBlocks [[m1],[m2]]
+
+instance Joinable Matrix Vector where
+    joinH m v = joinH m (asColumn v)
+    joinV m v = joinV m (asRow v)
+
+instance Joinable Vector Matrix where
+    joinH v m = joinH (asColumn v) m
+    joinV v m = joinV (asRow v) m
+
+infixl 4 <|>
+infixl 3 <->
+
+{- | Horizontal concatenation of matrices and vectors:
+
+@> (ident 3 -&- 3 * ident 3) |&| fromList [1..6.0]
+(6><4)
+ [ 1.0, 0.0, 0.0, 1.0
+ , 0.0, 1.0, 0.0, 2.0
+ , 0.0, 0.0, 1.0, 3.0
+ , 3.0, 0.0, 0.0, 4.0
+ , 0.0, 3.0, 0.0, 5.0
+ , 0.0, 0.0, 3.0, 6.0 ]@
+-}
+(<|>) :: (Field t, Joinable a b) => a t -> b t -> Matrix t
+a <|> b = joinH a b
+
+-- | Vertical concatenation of matrices and vectors.
+(<->) :: (Field t, Joinable a b) => a t -> b t -> Matrix t
+a <-> b = joinV a b