Define a custom 'Point' type instead of a 3-tuple so that its constructor can be...

[spline3.git] / src / Point.hs

diff --git a/src/Point.hs b/src/Point.hs
index fd3ac58dec3ceef5dfd5c8aa1615e25a9bc0af53..a334c5c95642ae1f06dea200d03546aa82418316 100644 (file)
--- a/src/Point.hs
+++ b/src/Point.hs
@@ -1,30 +1,47 @@
 {-# LANGUAGE FlexibleInstances #-}
 
 module Point (
-  Point,
+  Point(..),
   dot,
   scale
   )
 where
 
-type Point = (Double, Double, Double)
+import Test.QuickCheck (Arbitrary(..))
+
+
+-- | Represents a point in three dimensions. We use a custom type (as
+--   opposed to a 3-tuple) so that we can make the coordinates strict.
+data Point =
+  Point !Double !Double !Double
+  deriving (Eq, Show)
+
+
+instance Arbitrary Point where
+  arbitrary = do
+    (x,y,z) <- arbitrary
+    return $ Point x y z
+
 
 instance Num Point where
-    (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)
+  (Point x1 y1 z1) + (Point x2 y2 z2) = Point (x1+x2) (y1+y2) (z1+z2)
+  (Point x1 y1 z1) - (Point x2 y2 z2) = Point (x1-x2) (y1-y2) (z1-z2)
+  (Point x1 y1 z1) * (Point x2 y2 z2) = Point (x1*x2) (y1*y2) (z1*z2)
+  abs (Point x y z) = Point (abs x) (abs y) (abs z)
+  signum (Point x y z) = Point (signum x) (signum y) (signum z)
+  fromInteger n =
+    Point coord coord coord
+    where
+      coord = fromInteger n
 
 
 -- | Scale a point by a constant.
 scale :: Point -> Double -> Point
-scale (x, y, z) d = (x*d, y*d, z*d)
+scale (Point x y z) d = Point (x*d) (y*d) (z*d)
 
 
 -- | Returns the dot product of two points (taken as three-vectors).
 {-# INLINE dot #-}
 dot :: Point -> Point -> Double
-dot (x1, y1, z1) (x2, y2, z2) =
+dot (Point x1 y1 z1) (Point x2 y2 z2) =
     (x2 - x1)^(2::Int) + (y2 - y1)^(2::Int) + (z2 - z1)^(2::Int)