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diff --git a/ETL/ETL/_curve_func.h b/ETL/ETL/_curve_func.h
new file mode 100644
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+++ b/ETL/ETL/_curve_func.h
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+/*! ========================================================================
+** Extended Template and Library
+** Utility Curve Template Class Implementations
+** $Id$
+**
+** Copyright (c) 2002 Robert B. Quattlebaum Jr.
+**
+** This package is free software; you can redistribute it and/or
+** modify it under the terms of the GNU General Public License as
+** published by the Free Software Foundation; either version 2 of
+** the License, or (at your option) any later version.
+**
+** This package is distributed in the hope that it will be useful,
+** but WITHOUT ANY WARRANTY; without even the implied warranty of
+** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+** General Public License for more details.
+**
+** === N O T E S ===========================================================
+**
+** This is an internal header file, included by other ETL headers.
+** You should not attempt to use it directly.
+**
+** ========================================================================= */
+
+/* === S T A R T =========================================================== */
+
+#ifndef __ETL__CURVE_FUNC_H
+#define __ETL__CURVE_FUNC_H
+
+/* === H E A D E R S ======================================================= */
+
+#include <functional>
+
+/* -- C L A S S E S --------------------------------------------------------- */
+
+template <class T, class K=float>
+struct affine_combo
+{
+	// from (a) to (x) : x = a(1-t) + b(t)
+	T operator()(const T &a,const T &b,const K &t)const
+	{
+		return T( (b-a)*t+a );
+	}
+
+	// from (x) to (a) : a = (x-b(t)) / (1-t)
+	T reverse(const T &x, const T &b, const K &t)const
+	{
+		return T( (x-t*b)*(static_cast<K>(1)/(static_cast<K>(1)-t)) );
+	}
+};
+
+template <class T, class K=float>
+struct distance_func : public std::binary_function<T, T, K>
+{
+	K operator()(const T &a,const T &b)const
+	{
+		T delta=b-a;
+		return static_cast<K>(delta*delta);
+	}
+
+	K cook(const K &x)const { return x*x; }
+	K uncook(const K &x)const { return sqrt(x); }
+
+};
+
+/* -- E N D ----------------------------------------------------------------- */
+
+#endif