Add the 'dot' function for Points.

diff --git a/src/Point.hs b/src/Point.hs
index e5260ae06a943505e907439a4bff81ee7bbe03b8..95b33640f4e81406f71a685c617a3c273a2a6284 100644 (file)
--- a/src/Point.hs
+++ b/src/Point.hs
@@ -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,