X-Git-Url: http://gitweb.michael.orlitzky.com/?a=blobdiff_plain;f=src%2FTwoTuple.hs;h=3950fee9afeabd5bfb8d884ca6543c4689873c24;hb=1832912058bfe274e1f049dae80ea05daa94a1a1;hp=1b5e93e151f1f7d8b5f3774e454b4a4589c20b3b;hpb=c5da1efa77844ae6159dfc781ed886fdffbbf4d1;p=numerical-analysis.git

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.