parsed_fem_function_parameter.h

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// The libMesh Finite Element Library.
// Copyright (C) 2002-2023 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_PARSED_FEM_FUNCTION_PARAMETER_H
#define LIBMESH_PARSED_FEM_FUNCTION_PARAMETER_H


// Local Includes
#include "libmesh/libmesh_common.h"
#include "libmesh/parameter_accessor.h"

// C++ Includes
#include <memory>

namespace libMesh
{

// 前向声明
template <typename T> class ParsedFEMFunction;

template <typename T=Number>
class ParsedFEMFunctionParameter : public ParameterAccessor<T>
{
public:
  ParsedFEMFunctionParameter(ParsedFEMFunction<T> & func_ref,
                             std::string param_name) :
    _func(func_ref), _name(std::move(param_name)) {}

  virtual ParameterAccessor<T> &
  operator= (T * /* new_ptr */) { libmesh_error(); return *this; }

  virtual void set (const T & new_value) override {
    _func.set_inline_value(_name, new_value);
  }

  virtual const T & get () const override {
    _current_val = _func.get_inline_value(_name);
    return _current_val;
  }

  virtual std::unique_ptr<ParameterAccessor<T>> clone() const override {
    return std::make_unique<ParsedFEMFunctionParameter<T>>(_func, _name);
  }

private:
  ParsedFEMFunction<T> & _func;
  std::string _name;

  // 我们需要从 get() 返回一个引用。这对于 libMesh::Number 来说是毫无意义的，但在处理字段参数时可能会变得有意义。
  mutable libMesh::Number _current_val;
};

} // namespace libMesh

#endif // LIBMESH_PARSED_FEM_FUNCTION_PARAMETER_H