function_parser.h

// ---------------------------------------------------------------------
//
// Copyright (C) 2005 - 2019 by the deal.II authors
//
// This file is part of the deal.II library.
//
// The deal.II library is free software; you can use it, 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.
// The full text of the license can be found in the file LICENSE.md at
// the top level directory of deal.II.
//
// ---------------------------------------------------------------------

#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/exceptions.h>
#include <deal.II/base/point.h>
#include <deal.II/base/tensor.h>
#include <deal.II/base/thread_local_storage.h>

#include <map>
#include <memory>
#include <vector>

namespace mu
{
  class Parser;
}

DEAL_II_NAMESPACE_OPEN


template <typename>
class Vector;


template <int dim>
class FunctionParser : public AutoDerivativeFunction<dim>
{
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() override;

  using ConstMap = std::map<std::string, double>;

  using ConstMapIterator = ConstMap::iterator;

  void
  initialize(const std::string &             vars,
             const std::vector<std::string> &expressions,
             const ConstMap &                constants,
             const bool                      time_dependent = false);

  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;

  virtual void
  vector_value(const Point<dim> &p, Vector<double> &values) 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
                 << ").");


private:
#ifdef DEAL_II_WITH_MUPARSER

  mutable Threads::ThreadLocalStorage<std::vector<double>> vars;

  mutable Threads::ThreadLocalStorage<std::vector<std::unique_ptr<mu::Parser>>>
    fp;

  std::map<std::string, double> constants;

  std::vector<std::string> var_names;

  void
  init_muparser() const;
#endif

  std::vector<std::string> expressions;

  bool initialized;

  unsigned int n_vars;
};


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:
        Assert(false, ExcNotImplemented());
    }
  return "";
}



DEAL_II_NAMESPACE_CLOSE

#endif