X-Git-Url: https://git.pterodactylus.net/?a=blobdiff_plain;f=ETL%2Ftrunk%2FETL%2F_calculus.h;h=45c8ed48960378df1a83a173a9d958fc61f76b47;hb=9459638ad6797b8139f1e9f0715c96076dbf0890;hp=a9c95edc8601e10b37c56d62d246cd4ea9b2ad3b;hpb=36d01e1527fda602a9aed07d209eb34e6770bca8;p=synfig.git

diff --git a/ETL/trunk/ETL/_calculus.h b/ETL/trunk/ETL/_calculus.h
index a9c95ed..45c8ed4 100644
--- a/ETL/trunk/ETL/_calculus.h
+++ b/ETL/trunk/ETL/_calculus.h
@@ -4,6 +4,7 @@
 ** $Id$
 **
 ** Copyright (c) 2002 Robert B. Quattlebaum Jr.
+** Copyright (c) 2008 Chris Moore
 **
 ** This package is free software; you can redistribute it and/or
 ** modify it under the terms of the GNU General Public License as
@@ -28,14 +29,14 @@
 
 #include <functional>
 
+#include "hermite"
+
 /* === M A C R O S ========================================================= */
 
 //#ifndef _EPSILON
 //#define _EPSILON		0.0000001
 //#endif
 
-#define ETL_FIXED_DERIVATIVE 1
-
 /* === T Y P E D E F S ===================================================== */
 
 /* === C L A S S E S & S T R U C T S ======================================= */
@@ -53,11 +54,23 @@ public:
 	typename T::result_type
 	operator()(const typename T::argument_type &x)const
 	{
-#ifdef ETL_FIXED_DERIVATIVE
 		return (func(x+epsilon)-func(x))/epsilon;
-#else
-		return (func(x)-func(x+epsilon))/epsilon;
-#endif
+	}
+};
+
+template <typename T>
+class derivative<hermite<T> > : public std::unary_function<typename hermite<T>::argument_type,typename hermite<T>::result_type>
+{
+	hermite<T> func;
+public:
+	explicit derivative(const hermite<T> &x):func(x) { }
+
+	typename hermite<T>::result_type
+	operator()(const typename hermite<T>::argument_type &x)const
+	{
+		T a = func[0], b = func[1], c = func[2], d = func[3];
+		typename hermite<T>::argument_type y(1-x);
+		return ((b-a)*y*y + (c-b)*x*y*2 + (d-c)*x*x) * 3;
 	}
 };