Add bang patterns to the definition of Face (Ben Lippmeier).

[spline3.git] / src / Face.hs

diff --git a/src/Face.hs b/src/Face.hs
index 3f1c223e10b3d28516c1c052fe4532f96633adf0..bc316a72cee9ae4eb815424b2ccbfe8705316911 100644 (file)
--- a/src/Face.hs
+++ b/src/Face.hs
@@ -1,13 +1,16 @@
+-- | The Face module just contains the definition of the 'Face' data
+--   type and its two typeclass instances.
 module Face
+  ( Face(..) )
 where
 
 import Point
 import ThreeDimensional
 
-data Face = Face { v0 :: Point,
-                   v1 :: Point,
-                   v2 :: Point,
-                   v3 :: Point }
+data Face = Face { v0 :: !Point,
+                   v1 :: !Point,
+                   v2 :: !Point,
+                   v3 :: !Point }
           deriving (Eq)
 
 instance Show Face where
@@ -17,7 +20,16 @@ instance Show Face where
              "  v2: " ++ (show (v2 f)) ++ "\n" ++
              "  v3: " ++ (show (v3 f)) ++ "\n"
 
+-- | The 'Face' type is an instance of 'ThreeDimensional' so that we
+--   can call the 'center' function on it. This is useful because the
+--   center of a face is always a vertex of a tetrahedron.
 instance ThreeDimensional Face where
+    -- | Since a face is square, we can just average the four vertices
+    --   to find the center.
     center f = ((v0 f) + (v1 f) + (v2 f) + (v3 f)) `scale` (1/4)
-    -- Too lazy to implement this right now.
+
+    -- | It's possible to implement this, but it hasn't been done
+    --   yet. A face will contain a point if the point lies in the same
+    --   plane as the vertices of the face, and if it falls on the
+    --   correct side of the four sides of the face.
     contains_point _ _ = False