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diff --git a/include/2geom/numeric/symmetric-matrix-fs-operation.h b/include/2geom/numeric/symmetric-matrix-fs-operation.h
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+/*
+ * SymmetricMatrix basic operation
+ *
+ * Authors:
+ *      Marco Cecchetti <mrcekets at gmail.com>
+ *
+ * Copyright 2009  authors
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it either under the terms of the GNU Lesser General Public
+ * License version 2.1 as published by the Free Software Foundation
+ * (the "LGPL") or, at your option, under the terms of the Mozilla
+ * Public License Version 1.1 (the "MPL"). If you do not alter this
+ * notice, a recipient may use your version of this file under either
+ * the MPL or the LGPL.
+ *
+ * You should have received a copy of the LGPL along with this library
+ * in the file COPYING-LGPL-2.1; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ * You should have received a copy of the MPL along with this library
+ * in the file COPYING-MPL-1.1
+ *
+ * The contents of this file are subject to the Mozilla Public License
+ * Version 1.1 (the "License"); you may not use this file except in
+ * compliance with the License. You may obtain a copy of the License at
+ * http://www.mozilla.org/MPL/
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY
+ * OF ANY KIND, either express or implied. See the LGPL or the MPL for
+ * the specific language governing rights and limitations.
+ */
+
+#ifndef _NL_SYMMETRIC_MATRIX_FS_OPERATION_H_
+#define _NL_SYMMETRIC_MATRIX_FS_OPERATION_H_
+
+
+#include <2geom/numeric/symmetric-matrix-fs.h>
+#include <2geom/numeric/symmetric-matrix-fs-trace.h>
+
+
+
+
+namespace Geom { namespace NL {
+
+template <size_t N>
+SymmetricMatrix<N> adj(const ConstBaseSymmetricMatrix<N> & S);
+
+template <>
+inline
+SymmetricMatrix<2> adj(const ConstBaseSymmetricMatrix<2> & S)
+{
+    SymmetricMatrix<2> result;
+    result.get<0,0>() = S.get<1,1>();
+    result.get<1,0>() = -S.get<1,0>();
+    result.get<1,1>() = S.get<0,0>();
+    return result;
+}
+
+template <>
+inline
+SymmetricMatrix<3> adj(const ConstBaseSymmetricMatrix<3> & S)
+{
+    SymmetricMatrix<3> result;
+
+    result.get<0,0>() = S.get<1,1>() * S.get<2,2>() - S.get<1,2>() * S.get<2,1>();
+    result.get<1,0>() = S.get<0,2>() * S.get<2,1>() - S.get<0,1>() * S.get<2,2>();
+    result.get<1,1>() = S.get<0,0>() * S.get<2,2>() - S.get<0,2>() * S.get<2,0>();
+    result.get<2,0>() = S.get<0,1>() * S.get<1,2>() - S.get<0,2>() * S.get<1,1>();
+    result.get<2,1>() = S.get<0,2>() * S.get<1,0>() - S.get<0,0>() * S.get<1,2>();
+    result.get<2,2>() = S.get<0,0>() * S.get<1,1>() - S.get<0,1>() * S.get<1,0>();
+    return result;
+}
+
+template <size_t N>
+inline
+SymmetricMatrix<N> inverse(const ConstBaseSymmetricMatrix<N> & S)
+{
+    SymmetricMatrix<N> result = adj(S);
+    double d = det(S);
+    assert (d != 0);
+    result.scale (1/d);
+    return result;
+}
+
+} /* end namespace NL*/ } /* end namespace Geom*/
+
+
+#endif // _NL_SYMMETRIC_MATRIX_FS_OPERATION_H_
+
+
+
+
+/*
+  Local Variables:
+  mode:c++
+  c-file-style:"stroustrup"
+  c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
+  indent-tabs-mode:nil
+  fill-column:99
+  End:
+*/
+// vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:fileencoding=utf-8:textwidth=99 :