analytic_function.h

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// The libMesh Finite Element Library.
// Copyright (C) 2002-2026 Benjamin S. Kirk, John W. Peterson, Roy H. Stogner

// This library 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 2.1 of the License, or (at your option) any later version.

// This library 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 for more details.

// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA



#ifndef LIBMESH_ANALYTIC_FUNCTION_H
#define LIBMESH_ANALYTIC_FUNCTION_H

// Local Includes
#include "libmesh/function_base.h"

// C++ includes
#include <cstddef>

namespace libMesh
{

// Forward Declarations
template <typename T>
class DenseVector;

template <typename Output=Number>
class AnalyticFunction : public FunctionBase<Output>
{
public:

  typedef Output (*OutputFunction)(const Point & p, const Real time);

  AnalyticFunction (OutputFunction fptr);

  typedef void (*OutputVectorFunction)(DenseVector<Output> & output,
                                       const Point & p,
                                       const Real time);
  AnalyticFunction (OutputVectorFunction fptr);

  AnalyticFunction (AnalyticFunction &&) = default;
  AnalyticFunction (const AnalyticFunction &) = default;
  AnalyticFunction & operator= (const AnalyticFunction &) = default;
  AnalyticFunction & operator= (AnalyticFunction &&) = default;
  virtual ~AnalyticFunction () = default;

  OutputFunction _number_fptr;

  OutputVectorFunction _vector_fptr;

  virtual void init () override;

  virtual void clear () override;

  virtual std::unique_ptr<FunctionBase<Output>> clone () const override;

  virtual Output operator() (const Point & p,
                             const Real time=0.) override;

  virtual void operator() (const Point & p,
                           const Real time,
                           DenseVector<Output> & output) override;
};



// ------------------------------------------------------------
// AnalyticFunction inline methods
template <typename Output>
inline
Output AnalyticFunction<Output>::operator() (const Point & p,
                                             const Real time)
{
  libmesh_assert(this->initialized());
  libmesh_assert_msg(_number_fptr,
                     "You must construct AnalyticFunction with a scalar-valued "
                     "function in order to use this operator() override.");
  return (this->_number_fptr(p, time));
}



template <typename Output>
inline
void AnalyticFunction<Output>::operator() (const Point & p,
                                           const Real time,
                                           DenseVector<Output> & output)
{
  libmesh_assert(this->initialized());
  libmesh_assert_msg(_vector_fptr,
                     "You must construct AnalyticFunction with a vector-valued "
                     "function in order to use this operator() override.");
  this->_vector_fptr(output, p, time);
  return;
}



template <typename Output>
AnalyticFunction<Output>::AnalyticFunction (OutputFunction fptr) :
  FunctionBase<Output> (),
  _number_fptr (fptr),
  _vector_fptr (nullptr)
{
  libmesh_assert(fptr);
  this->_initialized = true;
}



template <typename Output>
inline
AnalyticFunction<Output>::AnalyticFunction (OutputVectorFunction fptr) :
  FunctionBase<Output> (),
  _number_fptr (nullptr),
  _vector_fptr (fptr)
{
  libmesh_assert(fptr);
  this->_initialized = true;
}



template <typename Output>
void AnalyticFunction<Output>::init ()
{
  // dumb double-test
  libmesh_assert ((_number_fptr != nullptr) || (_vector_fptr != nullptr));

  // definitely ready
  this->_initialized = true;
}



template <typename Output>
inline
void AnalyticFunction<Output>::clear ()
{
  // We probably need a method to reset these later...
  _number_fptr = nullptr;
  _vector_fptr = nullptr;

  // definitely not ready
  this->_initialized = false;
}



template <typename Output>
inline
std::unique_ptr<FunctionBase<Output>>
AnalyticFunction<Output>::clone () const
{
  return _number_fptr ?
    std::make_unique<AnalyticFunction<Output>>(_number_fptr) :
    std::make_unique<AnalyticFunction<Output>>(_vector_fptr);
}


} // namespace libMesh


#endif // LIBMESH_ANALYTIC_FUNCTION_H