X-Git-Url: http://gitweb.michael.orlitzky.com/?a=blobdiff_plain;f=src%2FPoint.hs;h=4b9eaece2c88173c7a634899207d877730a99c41;hb=3f7331f579118687cd73b977ce6aa7d401f88a09;hp=d0859bfc54208d9b096a4f876404a79682d6423e;hpb=89b8b6e94fcc944a1f4611811265f3c6217af850;p=spline3.git

diff --git a/src/Point.hs b/src/Point.hs
index d0859bf..4b9eaec 100644
--- a/src/Point.hs
+++ b/src/Point.hs
@@ -1,51 +1,46 @@
-{-# LANGUAGE TypeSynonymInstances #-}
-
-module Point
+{-# LANGUAGE FlexibleInstances #-}
+
+module Point (
+  Point,
+  distance,
+  dot,
+  is_close,
+  scale
+  )
 where
 
-type Point = (Double, Double, Double)
-
-x_coord :: Point -> Double
-x_coord (x, _, _) = x
+import Comparisons ((~=))
 
-y_coord :: Point -> Double
-y_coord (_, y, _) = y
 
-z_coord :: Point -> Double
-z_coord (_, _, z) = z
+type Point = (Double, Double, Double)
 
 instance Num Point where
-    p1 + p2 = (x1+x2, y1+y2, z1+z2)
-        where
-          x1 = x_coord p1
-          x2 = x_coord p2
-          y1 = y_coord p1
-          y2 = y_coord p2
-          z1 = z_coord p1
-          z2 = z_coord p2
-
-    p1 - p2 = (x1-x2, y1-y2, z1-z2)
-        where
-          x1 = x_coord p1
-          x2 = x_coord p2
-          y1 = y_coord p1
-          y2 = y_coord p2
-          z1 = z_coord p1
-          z2 = z_coord p2
-
-    p1 * p2 = (x1*x2, y1*y2, z1*z2)
-        where
-          x1 = x_coord p1
-          x2 = x_coord p2
-          y1 = y_coord p1
-          y2 = y_coord p2
-          z1 = z_coord p1
-          z2 = z_coord p2
-
+    (x1,y1,z1) + (x2,y2,z2) = (x1+x2, y1+y2, z1+z2)
+    (x1,y1,z1) - (x2,y2,z2) = (x1-x2, y1-y2, z1-z2)
+    (x1,y1,z1) * (x2,y2,z2) = (x1*x2, y1*y2, z1*z2)
     abs (x, y, z) = (abs x, abs y, abs z)
     signum (x, y, z) = (signum x, signum y, signum z)
     fromInteger n = (fromInteger n, fromInteger n, fromInteger n)
 
 
+-- | Scale a point by a constant.
 scale :: Point -> Double -> Point
 scale (x, y, z) d = (x*d, y*d, z*d)
+
+
+-- | Returns the distance between p1 and p2.
+distance :: Point -> Point -> Double
+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,
+--   'False' otherwise.
+is_close :: Point -> Point -> Bool
+is_close p1 p2 = (distance p1 p2) ~= 0