From c0ea15048f7c0285213e30c82b458504be10da91 Mon Sep 17 00:00:00 2001
From: Michael Orlitzky <michael@orlitzky.com>
Date: Thu, 1 Sep 2011 22:13:04 -0400
Subject: [PATCH] Speed up the Tetrahedron contains_point function by dropping
 the useless factor of its volume.

---
 src/Tetrahedron.hs | 26 ++++++++++++++++++++++----
 1 file changed, 22 insertions(+), 4 deletions(-)

diff --git a/src/Tetrahedron.hs b/src/Tetrahedron.hs
index 6c13f4b..95233e0 100644
--- a/src/Tetrahedron.hs
+++ b/src/Tetrahedron.hs
@@ -43,10 +43,28 @@ instance Show Tetrahedron where
 instance ThreeDimensional Tetrahedron where
     center t = ((v0 t) + (v1 t) + (v2 t) + (v3 t)) `scale` (1/4)
     contains_point t p =
-      (b0 t p) `nearly_ge` 0 &&
-      (b1 t p) `nearly_ge` 0 &&
-      (b2 t p) `nearly_ge` 0 &&
-      (b3 t p) `nearly_ge` 0
+      b0_unscaled `nearly_ge` 0 &&
+      b1_unscaled `nearly_ge` 0 &&
+      b2_unscaled `nearly_ge` 0 &&
+      b3_unscaled `nearly_ge` 0
+      where
+        -- Drop the useless division and volume calculation that we
+        -- would do if we used the regular b0,..b3 functions.
+        b0_unscaled :: Double
+        b0_unscaled = volume inner_tetrahedron
+          where inner_tetrahedron = t { v0 = p }
+
+        b1_unscaled :: Double
+        b1_unscaled = volume inner_tetrahedron
+          where inner_tetrahedron = t { v1 = p }
+
+        b2_unscaled :: Double
+        b2_unscaled = volume inner_tetrahedron
+          where inner_tetrahedron = t { v2 = p }
+
+        b3_unscaled :: Double
+        b3_unscaled = volume inner_tetrahedron
+          where inner_tetrahedron = t { v3 = p }
 
 
 polynomial :: Tetrahedron -> (RealFunction Point)
-- 
2.43.2