/usr/include/deal.II/base/parsed_function.h is in libdeal.ii-dev 8.4.2-2+b1.
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//
// Copyright (C) 2007 - 2015 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 at
// the top level of the deal.II distribution.
//
// ---------------------------------------------------------------------
#ifndef dealii__parsed_function_h
#define dealii__parsed_function_h
#include <deal.II/base/auto_derivative_function.h>
#include <deal.II/base/function_parser.h>
#include <deal.II/base/parameter_handler.h>
DEAL_II_NAMESPACE_OPEN
namespace Functions
{
/**
* Friendly interface to the FunctionParser class. This class is meant as a
* wrapper for the FunctionParser class. It is used in the step-34 tutorial
* program.
*
* It provides two methods to declare and parse a ParameterHandler object
* and creates the Function object declared in the parameter file. This
* class is derived from the AutoDerivativeFunction class, so you don't need
* to specify derivatives. An example of usage of this class is as follows:
*
* @code
* // A parameter handler
* ParameterHandler prm;
*
* // Declare a section for the function we need
* prm.enter_subsection("My vector function");
* ParsedFunction<dim>::declare_parameters(prm, dim);
* prm.leave_subsection();
*
* // Create a ParsedFunction
* ParsedFunction<dim> my_vector_function(dim);
*
* // Parse an input file.
* prm.read_input(some_input_file);
*
* // Initialize the ParsedFunction object with the given file
* prm.enter_subsection("My vector function");
* my_vector_function.parse_parameters(prm);
* prm.leave_subsection();
*
* @endcode
*
* And here is an example of how the input parameter could look like (see
* the documentation of the FunctionParser class for a detailed description
* of the syntax of the function definition):
*
* @code
*
* # A test two dimensional vector function, depending on time
* subsection My vector function
* set Function constants = kappa=.1, lambda=2.
* set Function expression = if(y>.5, kappa*x*(1-x),0); t^2*cos(lambda*pi*x)
* set Variable names = x,y,t
* end
*
* @endcode
*
* @ingroup functions
* @author Luca Heltai, 2006
*/
template <int dim>
class ParsedFunction : public AutoDerivativeFunction<dim>
{
public:
/**
* Construct a vector function. The vector function which is generated has
* @p n_components components (defaults to 1). The parameter @p h is used
* to initialize the AutoDerivativeFunction class from which this class is
* derived.
*/
ParsedFunction (const unsigned int n_components = 1, const double h=1e-8);
/**
* Declare parameters needed by this class. The additional parameter @p
* n_components is used to generate the right code according to the number
* of components of the function that will parse this ParameterHandler. If
* the number of components which is parsed does not match the number of
* components of this object, an assertion is thrown and the program is
* aborted. The default behavior for this class is to declare the
* following entries:
*
* @code
*
* set Function constants =
* set Function expression = 0
* set Variable names = x,y,t
*
* @endcode
*
*/
static void declare_parameters(ParameterHandler &prm,
const unsigned int n_components = 1);
/**
* Parse parameters needed by this class. If the number of components
* which is parsed does not match the number of components of this object,
* an assertion is thrown and the program is aborted. In order for the
* class to function properly, we follow the same conventions declared in
* the FunctionParser class (look there for a detailed description of the
* syntax for function declarations).
*
* The three variables that can be parsed from a parameter file are the
* following:
*
* @code
*
* set Function constants =
* set Function expression =
* set Variable names =
*
* @endcode
*
* Function constants is a collection of pairs in the form name=value,
* separated by commas, for example:
*
* @code
*
* set Function constants = lambda=1., alpha=2., gamma=3.
*
* @endcode
*
* These constants can be used in the declaration of the function
* expression, which follows the convention of the FunctionParser class.
* In order to specify vector functions, semicolons have to be used to
* separate the different components, e.g.:
*
* @code
*
* set Function expression = cos(pi*x) ; cos(pi*y)
*
* @endcode
*
* The variable names entry can be used to customize the name of the
* variables used in the Function. It defaults to
*
* @code
*
* set Variable names = x,t
*
* @endcode
*
* for one dimensional problems,
*
* @code
*
* set Variable names = x,y,t
*
* @endcode
*
* for two dimensional problems and
*
* @code
*
* set Variable names = x,y,z,t
*
* @endcode
*
* for three dimensional problems.
*
* The time variable can be set according to specifications in the
* FunctionTime base class.
*/
void parse_parameters(ParameterHandler &prm);
/**
* Return all components of a vector-valued function at the given point @p
* p.
*/
virtual void vector_value (const Point<dim> &p,
Vector<double> &values) const;
/**
* Return the value of the function at the given point. Unless there is
* only one component (i.e. the function is scalar), you should state the
* component you want to have evaluated; it defaults to zero, i.e. the
* first component.
*/
virtual double value (const Point< dim > &p,
const unsigned int component = 0) const;
/**
* Set the time to a specific value for time-dependent functions.
*
* We need to overwrite this to set the time also in the accessor
* FunctionParser<dim>.
*/
virtual void set_time(const double newtime);
private:
/**
* The object with which we do computations.
*/
FunctionParser<dim> function_object;
};
}
DEAL_II_NAMESPACE_CLOSE
#endif
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