function_parser.h

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// -----------------------------------------------------------------------------
//
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception OR LGPL-2.1-or-later
// Copyright (C) 2005 - 2026 by the deal.II authors
//
// This file is part of the deal.II library.
//
// Detailed license information governing the source code and contributions
// can be found in LICENSE.md and CONTRIBUTING.md at the top level directory.
//
// -----------------------------------------------------------------------------
 
#ifndef dealii_function_parser_h
#define dealii_function_parser_h
 
 
#include <deal.II/base/config.h>
 
#include <deal.II/base/auto_derivative_function.h>
#include <deal.II/base/mu_parser_internal.h>
#include <deal.II/base/point.h>
 
#include <map>
#include <vector>
 
DEAL_II_NAMESPACE_OPEN
 
// Forward declaration
#ifndef DOXYGEN
template <typename>
class Vector;
#endif
 
template <int dim>
class FunctionParser
  : public AutoDerivativeFunction<dim>,
    protected internal::FunctionParser::ParserImplementation<dim, double>
{
public:
  FunctionParser(const unsigned int n_components = 1,
                 const double       initial_time = 0.0,
                 const double       h            = 1e-8);
 
  FunctionParser(const std::string &expression,
                 const std::string &constants      = "",
                 const std::string &variable_names = default_variable_names() +
                                                     ",t",
                 const double h = 1e-8);
 
  FunctionParser(const FunctionParser &) = delete;
 
  FunctionParser(FunctionParser &&) = delete;
 
  FunctionParser &
  operator=(const FunctionParser &) = delete;
 
  FunctionParser &
  operator=(FunctionParser &&) = delete;
 
  using ConstMap = std::map<std::string, double>;
 
  virtual void
  initialize(const std::string              &vars,
             const std::vector<std::string> &expressions,
             const ConstMap                 &constants,
             const bool                      time_dependent = false) override;
 
  void
  initialize(const std::string &vars,
             const std::string &expression,
             const ConstMap    &constants,
             const bool         time_dependent = false);
 
  static std::string
  default_variable_names();
 
  virtual double
  value(const Point<dim> &p, const unsigned int component = 0) const override;
 
  const std::vector<std::string> &
  get_expressions() const;
 
  DeclException2(ExcParseError,
                 int,
                 std::string,
                 << "Parsing Error at Column " << arg1
                 << ". The parser said: " << arg2);
 
  DeclException2(ExcInvalidExpressionSize,
                 int,
                 int,
                 << "The number of components (" << arg1
                 << ") is not equal to the number of expressions (" << arg2
                 << ").");
 
};
 
 
template <int dim>
std::string
FunctionParser<dim>::default_variable_names()
{
  switch (dim)
    {
      case 1:
        return "x";
      case 2:
        return "x,y";
      case 3:
        return "x,y,z";
      default:
        DEAL_II_NOT_IMPLEMENTED();
    }
  return "";
}
 
 
 
DEAL_II_NAMESPACE_CLOSE
 
#endif