#include <deal.II/base/function.h>

Inheritance diagram for ScalarFunctionFromFunctionObject< dim, RangeNumberType >:

Public Member Functions
	ScalarFunctionFromFunctionObject (const std::function< RangeNumberType(const Point< dim > &)> &function_object)

virtual RangeNumberType	value (const Point< dim > &p, const unsigned int component=0) const

Public Member Functions inherited from Function< dim, RangeNumberType >
	Function (const unsigned int n_components=1, const RangeNumberType initial_time=0.0)

virtual	~Function ()=0

Function &	operator= (const Function &f)

virtual void	vector_value (const Point< dim > &p, Vector< RangeNumberType > &values) const

virtual void	value_list (const std::vector< Point< dim > > &points, std::vector< RangeNumberType > &values, const unsigned int component=0) const

virtual void	vector_value_list (const std::vector< Point< dim > > &points, std::vector< Vector< RangeNumberType > > &values) const

virtual void	vector_values (const std::vector< Point< dim > > &points, std::vector< std::vector< RangeNumberType > > &values) const

virtual Tensor< 1, dim, RangeNumberType >	gradient (const Point< dim > &p, const unsigned int component=0) const

virtual void	vector_gradient (const Point< dim > &p, std::vector< Tensor< 1, dim, RangeNumberType > > &gradients) const

virtual void	gradient_list (const std::vector< Point< dim > > &points, std::vector< Tensor< 1, dim, RangeNumberType > > &gradients, const unsigned int component=0) const

virtual void	vector_gradients (const std::vector< Point< dim > > &points, std::vector< std::vector< Tensor< 1, dim, RangeNumberType > > > &gradients) const

virtual void	vector_gradient_list (const std::vector< Point< dim > > &points, std::vector< std::vector< Tensor< 1, dim, RangeNumberType > > > &gradients) const

virtual RangeNumberType	laplacian (const Point< dim > &p, const unsigned int component=0) const

virtual void	vector_laplacian (const Point< dim > &p, Vector< RangeNumberType > &values) const

virtual void	laplacian_list (const std::vector< Point< dim > > &points, std::vector< RangeNumberType > &values, const unsigned int component=0) const

virtual void	vector_laplacian_list (const std::vector< Point< dim > > &points, std::vector< Vector< RangeNumberType > > &values) const

virtual SymmetricTensor< 2, dim, RangeNumberType >	hessian (const Point< dim > &p, const unsigned int component=0) const

virtual void	vector_hessian (const Point< dim > &p, std::vector< SymmetricTensor< 2, dim, RangeNumberType > > &values) const

virtual void	hessian_list (const std::vector< Point< dim > > &points, std::vector< SymmetricTensor< 2, dim, RangeNumberType > > &values, const unsigned int component=0) const

virtual void	vector_hessian_list (const std::vector< Point< dim > > &points, std::vector< std::vector< SymmetricTensor< 2, dim, RangeNumberType > > > &values) const

std::size_t	memory_consumption () const

Public Member Functions inherited from FunctionTime< RangeNumberType >
	FunctionTime (const RangeNumberType initial_time=RangeNumberType(0.0))

virtual	~FunctionTime ()=default

RangeNumberType	get_time () const

virtual void	set_time (const RangeNumberType new_time)

virtual void	advance_time (const RangeNumberType delta_t)

Public Member Functions inherited from Subscriptor
	Subscriptor ()

	Subscriptor (const Subscriptor &)

	Subscriptor (Subscriptor &&) noexcept

virtual	~Subscriptor ()

Subscriptor &	operator= (const Subscriptor &)

Subscriptor &	operator= (Subscriptor &&) noexcept

void	subscribe (const char *identifier=nullptr) const

void	unsubscribe (const char *identifier=nullptr) const

unsigned int	n_subscriptions () const

void	list_subscribers () const

template<class Archive >
void	serialize (Archive &ar, const unsigned int version)

Private Attributes
const std::function< RangeNumberType(const Point< dim > &)>	function_object

Additional Inherited Members
Static Public Member Functions inherited from Subscriptor
static ::ExceptionBase &	ExcInUse (int arg1, std::string arg2, std::string arg3)

static ::ExceptionBase &	ExcNoSubscriber (std::string arg1, std::string arg2)

Public Attributes inherited from Function< dim, RangeNumberType >
const unsigned int	n_components

Static Public Attributes inherited from Function< dim, RangeNumberType >
static const unsigned int	dimension = dim

Detailed Description

template<int dim, typename RangeNumberType = double>
class ScalarFunctionFromFunctionObject< dim, RangeNumberType >

This class provides a way to convert a scalar function of the kind

RangeNumberType foo (const Point<dim> &);

into an object of type Function<dim>. Since the argument returns a scalar, the result is clearly a Function object for which function.n_components==1. The class works by storing a pointer to the given function and every time function.value(p,component) is called, calls foo(p) and returns the corresponding value. It also makes sure that component is in fact zero, as needs be for scalar functions.

The class provides an easy way to turn a simple global function into something that has the required Function<dim> interface for operations like VectorTools::interpolate_boundary_values() etc., and thereby allows for simpler experimenting without having to write all the boiler plate code of declaring a class that is derived from Function and implementing the Function::value() function. An example of this is given in the results section of step-53.

The class gains additional expressive power because the argument it takes does not have to be a pointer to an actual function. Rather, it is a function object, i.e., it can also be the result of call to std::bind (or boost::bind) or some other object that can be called with a single argument. For example, if you need a Function object that returns the norm of a point, you could write it like so:

template <int dim, typename RangeNumberType>
class Norm : public Function<dim, RangeNumberType> {
  public:
    virtual RangeNumberType value (const Point<dim> &p,
                               const unsigned int component) const
    {
      Assert (component == 0, ExcMessage ("This object is scalar!"));
      return p.norm();
    }
 };
 Norm<2> my_norm_object;

and then pass the my_norm_object around, or you could write it like so:

ScalarFunctionFromFunctionObject<dim, RangeNumberType> my_norm_object (&Point<dim>::norm);

Similarly, to generate an object that computes the distance to a point q, we could do this:

template <int dim, typename RangeNumberType>
class DistanceTo : public Function<dim, RangeNumberType> {
  public:
    DistanceTo (const Point<dim> &q) : q(q) {}
    virtual RangeNumberType value (const Point<dim> &p,
                               const unsigned int component) const
    {
      Assert (component == 0, ExcMessage ("This object is scalar!"));
      return q.distance(p);
    }
  private:
    const Point<dim> q;
 };
 Point<2> q (2,3);
 DistanceTo<2> my_distance_object;

or we could write it like so:

ScalarFunctionFromFunctionObject<dim, RangeNumberType>
  my_distance_object (std::bind (&Point<dim>::distance,
                                       q,
                                       std::placeholders::_1));

The savings in work to write this are apparent.

Author: Wolfgang Bangerth, 2011

Definition at line 650 of file function.h.

Constructor & Destructor Documentation

◆ ScalarFunctionFromFunctionObject()

template<int dim, typename RangeNumberType = double>

ScalarFunctionFromFunctionObject< dim, RangeNumberType >::ScalarFunctionFromFunctionObject ( const std::function< RangeNumberType(const Point< dim > &)> & function_object )

Given a function object that takes a Point and returns a RangeNumberType value, convert this into an object that matches the Function<dim, RangeNumberType> interface.

Member Function Documentation

◆ value()

template<int dim, typename RangeNumberType = double>

virtual RangeNumberType ScalarFunctionFromFunctionObject< dim, RangeNumberType >::value	(	const Point< dim > &	p,
		const unsigned int	component = `0`
	)		const

virtual

Return the value of the function at the given point. Returns the value the function given to the constructor produces for this point.

Reimplemented from Function< dim, RangeNumberType >.

Member Data Documentation

◆ function_object

template<int dim, typename RangeNumberType = double>

const std::function<RangeNumberType (const Point<dim> &)> ScalarFunctionFromFunctionObject< dim, RangeNumberType >::function_object

private

The function object which we call when this class's value() or value_list() functions are called.

Definition at line 672 of file function.h.

The documentation for this class was generated from the following file:

deal.II/base/function.h

Public Member Functions

Private Attributes

Additional Inherited Members

Detailed Description

template<int dim, typename RangeNumberType = double> class ScalarFunctionFromFunctionObject< dim, RangeNumberType >

Constructor & Destructor Documentation

◆ ScalarFunctionFromFunctionObject()

Member Function Documentation

◆ value()

Member Data Documentation

◆ function_object

template<int dim, typename RangeNumberType = double>
class ScalarFunctionFromFunctionObject< dim, RangeNumberType >