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// This file is part of Eigen, a lightweight C++ template library
// for linear algebra. Eigen itself is part of the KDE project.
//
// Copyright (C) 2006-2007 Benoit Jacob <jacob@math.jussieu.fr>
//
// Eigen 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 or (at your option) any later version.
//
// Eigen 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.
//
// You should have received a copy of the GNU General Public License along
// with Eigen; if not, write to the Free Software Foundation, Inc., 51
// Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
//
// As a special exception, if other files instantiate templates or use macros
// or functions from this file, or you compile this file and link it
// with other works to produce a work based on this file, this file does not
// by itself cause the resulting work to be covered by the GNU General Public
// License. This exception does not invalidate any other reasons why a work
// based on this file might be covered by the GNU General Public License.
#ifndef EIGEN_EVAL_H
#define EIGEN_EVAL_H
/** \class Eval
*
* \brief Evaluation of an expression
*
* The template parameter Expression is the type of the expression that we are evaluating.
*
* This class is the return
* type of MatrixBase::eval() and most of the time this is the only way it
* is used.
*
* However, if you want to write a function returning an evaluation of an expression, you
* will need to use this class.
*
* Here is an example illustrating this:
* \include class_Eval.cpp
* Output: \verbinclude class_Eval.out
*
* \sa MatrixBase::eval()
*/
template<typename Expression> class Eval : NoOperatorEquals,
public Matrix< typename Expression::Scalar,
Expression::RowsAtCompileTime,
Expression::ColsAtCompileTime >
{
public:
typedef typename Expression::Scalar Scalar;
typedef Matrix<Scalar, Expression::RowsAtCompileTime, Expression::ColsAtCompileTime> MatrixType;
typedef Expression Base;
friend class MatrixBase<Scalar, Expression>;
Eval(const Expression& expression) : MatrixType(expression) {}
};
/** Evaluates *this, which can be any expression, and returns the obtained matrix.
*
* A common use case for this is the following. In an expression-templates library
* like Eigen, the coefficients of an expression are only computed as they are
* accessed, they are not computed when the expression itself is constructed. This is
* usually a good thing, as this "lazy evaluation" improves performance, but can also
* in certain cases lead to wrong results and/or to redundant computations. In such
* cases, one can restore the classical immediate-evaluation behavior by calling eval().
*
* Example: \include MatrixBase_eval.cpp
* Output: \verbinclude MatrixBase_eval.out
*
* \sa class Eval */
template<typename Scalar, typename Derived>
const Eval<Derived> MatrixBase<Scalar, Derived>::eval() const
{
return Eval<Derived>(*static_cast<const Derived*>(this));
}
#endif // EIGEN_EVAL_H
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