From: Michael Orlitzky <michael@orlitzky.com>
Date: Wed, 17 Oct 2012 21:25:31 +0000 (-0400)
Subject: Rename "norm" to "norm_2" in the Vector class.
X-Git-Url: http://gitweb.michael.orlitzky.com/?p=numerical-analysis.git;a=commitdiff_plain;h=1832912058bfe274e1f049dae80ea05daa94a1a1

Rename "norm" to "norm_2" in the Vector class.
Add "norm_infty" to the Vector class.
---

diff --git a/src/TwoTuple.hs b/src/TwoTuple.hs
index 1b5e93e..3950fee 100644
--- a/src/TwoTuple.hs
+++ b/src/TwoTuple.hs
@@ -21,7 +21,14 @@ instance Functor TwoTuple where
 instance (RealFloat a) => Vector (TwoTuple a) where
   -- The standard Euclidean 2-norm. We need RealFloat for the square
   -- root.
-  norm (TwoTuple x1 y1) = fromRational $ toRational (sqrt(x1^2 + y1^2))
+  norm_2 (TwoTuple x y) = fromRational $ toRational (sqrt(x^2 + y^2))
+
+  -- The infinity norm, i.e. the maximum entry.
+  norm_infty (TwoTuple x y) =
+    fromRational $ max absx absy
+    where
+      absx = abs (toRational x)
+      absy = abs (toRational y)
 
 -- | It's not correct to use Num here, but I really don't want to have
 --   to define my own addition and subtraction.
diff --git a/src/Vector.hs b/src/Vector.hs
index 97bb5d8..6953031 100644
--- a/src/Vector.hs
+++ b/src/Vector.hs
@@ -8,17 +8,22 @@ where
 import Data.Number.BigFloat
 
 class (Num a) => Vector a where
-  norm :: RealFrac b => a -> b
+  norm_2 :: RealFrac b => a -> b
+  norm_infty :: RealFrac b => a -> b
 
 -- Define instances for common numeric types.
 instance Vector Integer where
-  norm = fromInteger
+  norm_2 = fromInteger
+  norm_infty = fromInteger
 
 instance Vector Rational where
-  norm = fromRational
+  norm_2 = fromRational
+  norm_infty = fromRational
 
 instance Epsilon e => Vector (BigFloat e) where
-  norm = fromRational . toRational
+  norm_2 = fromRational . toRational
+  norm_infty = fromRational . toRational
 
 instance Vector Double where
-  norm = fromRational . toRational
+  norm_2 = fromRational . toRational
+  norm_infty = fromRational . toRational