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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) 2006-2008 Benoit Jacob <jacob@math.jussieu.fr>
//
// Eigen is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 3 of the License, or (at your option) any later version.
//
// Alternatively, 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.
//
// 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 Lesser General Public License or the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License and a copy of the GNU General Public License along with
// Eigen. If not, see <http://www.gnu.org/licenses/>.
#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 ExpressionType>
struct ei_traits<Eval<ExpressionType> >
{
typedef typename ExpressionType::Scalar Scalar;
enum {
RowsAtCompileTime = ExpressionType::RowsAtCompileTime,
ColsAtCompileTime = ExpressionType::ColsAtCompileTime,
MaxRowsAtCompileTime = ExpressionType::MaxRowsAtCompileTime,
MaxColsAtCompileTime = ExpressionType::MaxColsAtCompileTime,
Flags = ExpressionType::Flags & ~LazyBit
};
};
template<typename ExpressionType> class Eval : ei_no_assignment_operator,
public Matrix< typename ExpressionType::Scalar,
ExpressionType::RowsAtCompileTime,
ExpressionType::ColsAtCompileTime,
ExpressionType::Flags,
ExpressionType::MaxRowsAtCompileTime,
ExpressionType::MaxColsAtCompileTime>
{
public:
/** The actual matrix type to evaluate to. This type can be used independently
* of the rest of this class to get the actual matrix type to evaluate and store
* the value of an expression.
*
* Here is an example illustrating this:
* \include Eval_MatrixType.cpp
* Output: \verbinclude Eval_MatrixType.out
*/
typedef Matrix<typename ExpressionType::Scalar,
ExpressionType::RowsAtCompileTime,
ExpressionType::ColsAtCompileTime,
ExpressionType::Flags,
ExpressionType::MaxRowsAtCompileTime,
ExpressionType::MaxColsAtCompileTime> MatrixType;
_EIGEN_GENERIC_PUBLIC_INTERFACE(Eval, MatrixType)
explicit Eval(const ExpressionType& expr) : MatrixType(expr) {}
};
/** 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 Derived>
const typename ei_eval_unless_lazy<Derived>::type MatrixBase<Derived>::eval() const
{
return typename ei_eval_unless_lazy<Derived>::type(derived());
}
#endif // EIGEN_EVAL_H
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