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// ------------------------------------------------------------------------
//
// SPDX-License-Identifier: LGPL-2.1-or-later
// Copyright (C) 2010 - 2025 by the deal.II authors
//
// This file is part of the deal.II library.
//
// Part of the source code is dual licensed under Apache-2.0 WITH
// LLVM-exception OR LGPL-2.1-or-later. Detailed license information
// governing the source code and code contributions can be found in
// LICENSE.md and CONTRIBUTING.md at the top level directory of deal.II.
//
// ------------------------------------------------------------------------
#ifndef dealii_function_bessel_h
#define dealii_function_bessel_h
#include <deal.II/base/config.h>
#include <deal.II/base/function.h>
#include <deal.II/base/point.h>
#include <vector>
DEAL_II_NAMESPACE_OPEN
namespace Functions
{
/**
* The Bessel functions of first kind or positive integer order.
*
* @ingroup functions
*/
template <int dim>
class Bessel1 : public Function<dim>
{
public:
/**
* Constructor. @p wave_number must be nonnegative.
*/
Bessel1(const unsigned int order,
const double wave_number,
const Point<dim> center = Point<dim>());
virtual double
value(const Point<dim> &points,
const unsigned int component = 0) const override;
virtual void
value_list(const std::vector<Point<dim>> &points,
std::vector<double> &values,
const unsigned int component = 0) const override;
virtual Tensor<1, dim>
gradient(const Point<dim> &p,
const unsigned int component = 0) const override;
virtual void
gradient_list(const std::vector<Point<dim>> &points,
std::vector<Tensor<1, dim>> &gradients,
const unsigned int component = 0) const override;
private:
unsigned int order;
double wave_number;
Point<dim> center;
};
} // namespace Functions
DEAL_II_NAMESPACE_CLOSE
#endif
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