Remove .gitignore do nothing is ignored.

[synfig.git] / ETL / trunk / ETL / _calculus.h

diff --git a/ETL/trunk/ETL/_calculus.h b/ETL/trunk/ETL/_calculus.h
index a9c95ed..45c8ed4 100644 (file)
--- 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;
        }
 };