function_base.h

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// The libMesh Finite Element Library.
// Copyright (C) 2002-2024 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_FUNCTION_BASE_H
#define LIBMESH_FUNCTION_BASE_H

// Local Includes
#include "libmesh/libmesh_common.h"
#include "libmesh/dense_vector.h" // required to instantiate a DenseVector<> below

// C++ includes
#include <cstddef>
#include <memory>

namespace libMesh
{

// Forward Declarations
class Point;

template <typename Output=Number>
class FunctionBase
{
protected:

  explicit
  FunctionBase (const FunctionBase * master = nullptr);

public:

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

  virtual void init () {}

  virtual void clear () {}

  virtual std::unique_ptr<FunctionBase<Output>> clone () const = 0;

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

  void operator() (const Point & p,
                   DenseVector<Output> & output);

  virtual void operator() (const Point & p,
                           const Real time,
                           DenseVector<Output> & output) = 0;

  virtual Output component(unsigned int i,
                           const Point & p,
                           Real time=0.);


  bool initialized () const;

  void set_is_time_dependent( bool is_time_dependent);

  bool is_time_dependent() const;

protected:

  const FunctionBase * _master;

  bool _initialized;

  bool _is_time_dependent;

};


// ------------------------------------------------------------
// FunctionBase inline methods

template<typename Output>
inline
FunctionBase<Output>::FunctionBase (const FunctionBase * master) :
  _master             (master),
  _initialized        (false),
  _is_time_dependent  (true) // Assume we are time-dependent until the user says otherwise
{
}



template <typename Output>
inline
bool FunctionBase<Output>::initialized() const
{
  return (this->_initialized);
}

template <typename Output>
inline
void FunctionBase<Output>::set_is_time_dependent( bool is_time_dependent )
{
  this->_is_time_dependent = is_time_dependent;
}

template <typename Output>
inline
bool FunctionBase<Output>::is_time_dependent() const
{
  return (this->_is_time_dependent);
}


template <typename Output>
inline
Output FunctionBase<Output>::component (unsigned int i,
                                        const Point & p,
                                        Real time)
{
  DenseVector<Output> outvec(i+1);
  (*this)(p, time, outvec);
  return outvec(i);
}



template <typename Output>
inline
void FunctionBase<Output>::operator() (const Point & p,
                                       DenseVector<Output> & output)
{
  // Call the time-dependent function with t=0.
  this->operator()(p, 0., output);
}

} // namespace libMesh

#endif // LIBMESH_FUNCTION_BASE_H