X-Git-Url: http://gitweb.michael.orlitzky.com/?a=blobdiff_plain;f=src%2FPoint.hs;h=95b33640f4e81406f71a685c617a3c273a2a6284;hb=1d371234dc06d20b59d8b42a46e42aebf430b9f4;hp=2b8d59736e28e91a5ce1cc9104e5c131305db3c6;hpb=603d9155a29bfbc353b42a6c880edce224626a16;p=spline3.git

diff --git a/src/Point.hs b/src/Point.hs
index 2b8d597..95b3364 100644
--- a/src/Point.hs
+++ b/src/Point.hs
@@ -1,4 +1,4 @@
-{-# LANGUAGE TypeSynonymInstances #-}
+{-# LANGUAGE FlexibleInstances #-}
 
 module Point
 where
@@ -24,8 +24,14 @@ scale (x, y, z) d = (x*d, y*d, z*d)
 
 -- | Returns the distance between p1 and p2.
 distance :: Point -> Point -> Double
-distance (x1, y1, z1) (x2, y2, z2) =
-    sqrt $ (x2 - x1)^(2::Int) + (y2 - y1)^(2::Int) + (z2 - z1)^(2::Int)
+distance p1 p2 =
+    sqrt $ p1 `dot` p2
+
+
+-- | Returns the dot product of two points (taken as three-vectors).
+dot :: Point -> Point -> Double
+dot (x1, y1, z1) (x2, y2, z2) =
+    (x2 - x1)^(2::Int) + (y2 - y1)^(2::Int) + (z2 - z1)^(2::Int)
 
 
 -- | Returns 'True' if p1 is close to (within 'epsilon' of) p2,