Reference documentation for deal.II version Git 1dafe5d 2017-11-23 14:01:03 +0100
Public Member Functions | Private Attributes | List of all members
ScalarFunctionFromFunctionObject< dim, RangeNumberType > Class Template Reference

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

Inheritance diagram for ScalarFunctionFromFunctionObject< dim, RangeNumberType >:
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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
 
Functionoperator= (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 RangeNumberTypeinitial_time=RangeNumberType(0.0))
 
virtual ~FunctionTime ()=default
 
RangeNumberType get_time () const
 
virtual void set_time (const RangeNumberTypenew_time)
 
virtual void advance_time (const RangeNumberTypedelta_t)
 
- Public Member Functions inherited from Subscriptor
 Subscriptor ()
 
 Subscriptor (const Subscriptor &)
 
 Subscriptor (Subscriptor &&)
 
virtual ~Subscriptor ()
 
Subscriptoroperator= (const Subscriptor &)
 
Subscriptoroperator= (Subscriptor &&)
 
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, char *arg2, std::string &arg3)
 
static::ExceptionBase & ExcNoSubscriber (char *arg1, char *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:

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:

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

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

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

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: