More doc updates.

[spline3.git] / src / Point.hs

diff --git a/src/Point.hs b/src/Point.hs
index d0859bfc54208d9b096a4f876404a79682d6423e..bf6fe8ea9a2f6fc4e3ce59168cd7ce798981e894 100644 (file)
--- a/src/Point.hs
+++ b/src/Point.hs
@@ -3,6 +3,9 @@
 module Point
 where
 
+import Comparisons
+
+
 type Point = (Double, Double, Double)
 
 x_coord :: Point -> Double
@@ -47,5 +50,25 @@ instance Num Point where
     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 $ (x2 - x1)^(2::Int) + (y2 - y1)^(2::Int) + (z2 - z1)^(2::Int)
+    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
+
+
+-- | 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