From a96be0c7818e0408b4aac9076df131c5b3ec6ff4 Mon Sep 17 00:00:00 2001
From: Michael Orlitzky <michael@orlitzky.com>
Date: Fri, 7 Feb 2014 18:56:21 -0500
Subject: [PATCH] Drop the 'column' function that returned a vector instead of
 a matrix.

---
 src/Linear/Matrix.hs | 22 +++++++++++-----------
 src/Linear/QR.hs     |  8 ++++----
 2 files changed, 15 insertions(+), 15 deletions(-)

diff --git a/src/Linear/Matrix.hs b/src/Linear/Matrix.hs
index 054bb6e..6d13a69 100644
--- a/src/Linear/Matrix.hs
+++ b/src/Linear/Matrix.hs
@@ -188,24 +188,23 @@ row' m i =
 
 
 -- | Return the @j@th column of @m@. Unsafe.
-column :: Mat m n a -> Int -> (Vec m a)
-column (Mat rows) j =
-  V.map (element j) rows
-  where
-    element = flip (!)
+--column :: Mat m n a -> Int -> (Vec m a)
+--column (Mat rows) j =
+--  V.map (element j) rows
+--  where
+--    element = flip (!)
 
 
 -- | Return the @j@th column of @m@ as a matrix. Unsafe.
-column' :: (Arity m, Arity n) => Mat m n a -> Int -> Col m a
-column' m j =
+column :: (Arity m, Arity n) => Mat m n a -> Int -> Col m a
+column m j =
   construct lambda
   where
     lambda i _ = m !!! (i, j)
 
 
 -- | Transpose @m@; switch it's columns and its rows. This is a dirty
---   implementation.. it would be a little cleaner to use imap, but it
---   doesn't seem to work.
+--   implementation, but I don't see a better way.
 --
 --   TODO: Don't cheat with fromList.
 --
@@ -216,9 +215,10 @@ column' m j =
 --   ((1,3),(2,4))
 --
 transpose :: (Arity m, Arity n) => Mat m n a -> Mat n m a
-transpose m = Mat $ V.fromList column_list
+transpose matrix =
+  construct lambda
   where
-    column_list = [ column m i | i <- [0..(ncols m)-1] ]
+    lambda i j = matrix !!! (j,i)
 
 
 -- | Is @m@ symmetric?
diff --git a/src/Linear/QR.hs b/src/Linear/QR.hs
index 043b172..8d9ea42 100644
--- a/src/Linear/QR.hs
+++ b/src/Linear/QR.hs
@@ -231,7 +231,7 @@ eigenvalues iterations matrix
 --   Examples:
 --
 --   >>> import Linear.Matrix ( Col2, Col3, Mat2, Mat3 )
---   >>> import Linear.Matrix ( column', frobenius_norm, fromList )
+--   >>> import Linear.Matrix ( column, frobenius_norm, fromList )
 --   >>> import Linear.Matrix ( identity_matrix, vec3d )
 --   >>> import Normed ( Normed(..) )
 --
@@ -253,11 +253,11 @@ eigenvalues iterations matrix
 --   >>> let v1  = (1 / (norm v1') :: Double) *> v1'
 --   >>> let v2' = vec3d (-4, -2, 5) :: Col3 Double
 --   >>> let v2  = (1 / (norm v2') :: Double) *> v2'
---   >>> frobenius_norm ((column' vecs 0) - v0) < 1e-12
+--   >>> frobenius_norm ((column vecs 0) - v0) < 1e-12
 --   True
---   >>> frobenius_norm ((column' vecs 1) - v1) < 1e-12
+--   >>> frobenius_norm ((column vecs 1) - v1) < 1e-12
 --   True
---   >>> frobenius_norm ((column' vecs 2) - v2) < 1e-12
+--   >>> frobenius_norm ((column vecs 2) - v2) < 1e-12
 --   True
 --
 eigenvectors_symmetric :: forall m a. (Arity m, Algebraic.C a, Eq a)
-- 
2.43.2