deal.II and the C++11 standard

Namespaces
	std_cxx11

Classes
class	IteratorRange< Iterator >

Cell iterator functions returning ranges of iterators
IteratorRange< cell_iterator >	DoFHandler< dim, spacedim >::cell_iterators () const
IteratorRange< active_cell_iterator >	DoFHandler< dim, spacedim >::active_cell_iterators () const
IteratorRange< level_cell_iterator >	DoFHandler< dim, spacedim >::mg_cell_iterators () const
IteratorRange< cell_iterator >	DoFHandler< dim, spacedim >::cell_iterators_on_level (const unsigned int level) const
IteratorRange< active_cell_iterator >	DoFHandler< dim, spacedim >::active_cell_iterators_on_level (const unsigned int level) const
IteratorRange< level_cell_iterator >	DoFHandler< dim, spacedim >::mg_cell_iterators_on_level (const unsigned int level) const

Cell iterator functions returning ranges of iterators
IteratorRange< cell_iterator >	Triangulation< dim, spacedim >::cell_iterators () const
IteratorRange< active_cell_iterator >	Triangulation< dim, spacedim >::active_cell_iterators () const
IteratorRange< cell_iterator >	Triangulation< dim, spacedim >::cell_iterators_on_level (const unsigned int level) const
IteratorRange< active_cell_iterator >	Triangulation< dim, spacedim >::active_cell_iterators_on_level (const unsigned int level) const

Cell iterator functions returning ranges of iterators
IteratorRange< cell_iterator >	hp::DoFHandler< dim, spacedim >::cell_iterators () const
IteratorRange< active_cell_iterator >	hp::DoFHandler< dim, spacedim >::active_cell_iterators () const
IteratorRange< cell_iterator >	hp::DoFHandler< dim, spacedim >::cell_iterators_on_level (const unsigned int level) const
IteratorRange< active_cell_iterator >	hp::DoFHandler< dim, spacedim >::active_cell_iterators_on_level (const unsigned int level) const

Detailed Description

At present, deal.II only requires a compiler that conforms to the C++98 standard and does not rely on compilers to either provide the features introduced in C++03 or C++11

That said, deal.II interfaces with C++11 in several ways as outlined below.

Use of C++11 classes and substitution by BOOST

deal.II makes use of many of the classes that were only added as part of C++11. This includes std::shared_ptr, std::function, std::bind, std::tuple and a number of others. Because we do not assume that the compiler actually supports C++11, there needs to be a way to ensure that these classes are available also for pre-C++11 compilers. This is done using the following approach:

• We create a namespace std_cxx11.
• If the compiler supports C++11, we import the relevant classes and functions into this namespace using statements such as

  namespace std_cxx11 {  using std::shared_ptr;  }

• If the compiler does not support C++11, if its support for C++11 is incomplete, or if it is buggy, then we use as a fallback the corresponding classes and functions provided by the BOOST library through statements such as

  namespace std_cxx11 {  using boost::shared_ptr;  }

Consequently, namespace std_cxx11 contains all of the symbols we require. The classes that can be used this way are obviously a subset of the intersection between C++11 and what BOOST provides.

Support for C++11 range-based for loops

C++11 provides many new core language features, such as rvalue references and move semantics, initialized lists, tuples, variadic templates and others. For a complete list, see http://en.wikipedia.org/wiki/C++11 . We can not use most of these in deal.II itself because we cannot rely on compilers supporting them.

However, this does not preclude users from using such features in their own applications if they can be reasonably sure that the compilers on all of the systems they will work on do support C++11. An example are automatically typed variables.

deal.II does provide some features that make programming simpler when using C++11. This is true, in particular, for range-based for loops. deal.II-based codes often have many loops of the kind

Triangulation<dim> triangulation;
...
typename Triangulation<dim>::active_cell_iterator
  cell = triangulation.begin_active(),
  endc = triangulation.end();
for (; cell!=endc; ++cell)
  cell->set_refine_flag();

Using C++11's range-based for loops, you can now write this as follows:

Triangulation<dim> triangulation;
...
for (auto cell : triangulation.active_cell_iterators())
  cell->set_refine_flag();

This relies on functions such as Triangulation::active_cell_iterators(), and equivalents in the DoF handler classes, DoFHandler::active_cell_iterators(), hp::DoFHandler::active_cell_iterators(). There are variants of these functions that provide iterator ranges for all cells (not just the active ones) and for cells on individual levels.

Things that are only enabled if your compiler supports C++11

There is a small number of places inside deal.II where we allow ourselves the use of C++11 because it makes things so much simpler. These features are simply not available if your compiler does not support C++11, but this does not affect the usability of the remainder of deal.II.

Specifically, these places are:

• The LinearOperator class and all associated functions such as linear_operator(), null_operator(), and everything else that is part of the LAOperators documentation module.

Function Documentation

cell_iterators() [1/3]

template<int dim, int spacedim>

IteratorRange< typename DoFHandler< dim, spacedim >::cell_iterator > DoFHandler< dim, spacedim >::cell_iterators

(

)

const

Return an iterator range that contains all cells (active or not) that make up this DoFHandler. Such a range is useful to initialize range-based for loops as supported by C++11. See the example in the documentation of active_cell_iterators().

Returns

The half open range [this->begin(), this->end())

Definition at line 930 of file dof_handler.cc.

active_cell_iterators() [1/3]

template<int dim, int spacedim>

IteratorRange< typename DoFHandler< dim, spacedim >::active_cell_iterator > DoFHandler< dim, spacedim >::active_cell_iterators

(

)

const

Return an iterator range that contains all active cells that make up this DoFHandler. Such a range is useful to initialize range-based for loops as supported by C++11, see also C++11 standard.

Range-based for loops are useful in that they require much less code than traditional loops (see here for a discussion of how they work). An example is that without range-based for loops, one often writes code such as the following:

DoFHandler<dim> dof_handler;
...
typename DoFHandler<dim>::active_cell_iterator
  cell = dof_handler.begin_active(),
  endc = dof_handler.end();
for (; cell!=endc; ++cell)
  {
    fe_values.reinit (cell);
    ...do the local integration on 'cell'...;
  }

Using C++11's range-based for loops, this is now entirely equivalent to the following:

DoFHandler<dim> dof_handler;
...
for (auto cell : dof_handler.active_cell_iterators())
  {
    fe_values.reinit (cell);
    ...do the local integration on 'cell'...;
  }

To use this feature, you need a compiler that supports C++11.

Returns

The half open range [this->begin_active(), this->end())

Definition at line 940 of file dof_handler.cc.

mg_cell_iterators()

template<int dim, int spacedim>

IteratorRange< typename DoFHandler< dim, spacedim >::level_cell_iterator > DoFHandler< dim, spacedim >::mg_cell_iterators

(

)

const

Return an iterator range that contains all cells (active or not) that make up this DoFHandler in their level-cell form. Such a range is useful to initialize range-based for loops as supported by C++11. See the example in the documentation of active_cell_iterators().

Returns

The half open range [this->begin_mg(), this->end_mg())

Definition at line 951 of file dof_handler.cc.

cell_iterators_on_level() [1/3]

template<int dim, int spacedim>

IteratorRange< typename DoFHandler< dim, spacedim >::cell_iterator > DoFHandler< dim, spacedim >::cell_iterators_on_level

(

const unsigned int

level

)

const

Return an iterator range that contains all cells (active or not) that make up the given level of this DoFHandler. Such a range is useful to initialize range-based for loops as supported by C++11. See the example in the documentation of active_cell_iterators().

Parameters

[in]

level

A given level in the refinement hierarchy of this triangulation.

Returns

The half open range [this->begin(level), this->end(level))

Precondition

level must be less than this->n_levels().

Definition at line 963 of file dof_handler.cc.

active_cell_iterators_on_level() [1/3]

template<int dim, int spacedim>

IteratorRange< typename DoFHandler< dim, spacedim >::active_cell_iterator > DoFHandler< dim, spacedim >::active_cell_iterators_on_level

(

const unsigned int

level

)

const

Return an iterator range that contains all active cells that make up the given level of this DoFHandler. Such a range is useful to initialize range-based for loops as supported by C++11. See the example in the documentation of active_cell_iterators().

Parameters

[in]

level

A given level in the refinement hierarchy of this triangulation.

Returns

The half open range [this->begin_active(level), this->end(level))

Precondition

level must be less than this->n_levels().

Definition at line 974 of file dof_handler.cc.

mg_cell_iterators_on_level()

template<int dim, int spacedim>

IteratorRange< typename DoFHandler< dim, spacedim >::level_cell_iterator > DoFHandler< dim, spacedim >::mg_cell_iterators_on_level

(

const unsigned int

level

)

const

Return an iterator range that contains all cells (active or not) that make up the given level of this DoFHandler in their level-cell form. Such a range is useful to initialize range-based for loops as supported by C++11. See the example in the documentation of active_cell_iterators().

Parameters

[in]

level

A given level in the refinement hierarchy of this triangulation.

Returns

The half open range [this->begin_mg(level), this->end_mg(level))

Precondition

level must be less than this->n_levels().

Definition at line 985 of file dof_handler.cc.

cell_iterators() [2/3]

template<int dim, int spacedim>

IteratorRange< typename Triangulation< dim, spacedim >::cell_iterator > Triangulation< dim, spacedim >::cell_iterators

(

)

const

Return an iterator range that contains all cells (active or not) that make up this triangulation. Such a range is useful to initialize range- based for loops as supported by C++11. See the example in the documentation of active_cell_iterators().

Returns

The half open range [this->begin(), this->end())

Definition at line 10511 of file tria.cc.

active_cell_iterators() [2/3]

template<int dim, int spacedim>

IteratorRange< typename Triangulation< dim, spacedim >::active_cell_iterator > Triangulation< dim, spacedim >::active_cell_iterators

(

)

const

Return an iterator range that contains all active cells that make up this triangulation. Such a range is useful to initialize range-based for loops as supported by C++11, see also C++11 standard.

Range-based for loops are useful in that they require much less code than traditional loops (see here for a discussion of how they work). An example is that without range-based for loops, one often writes code such as the following (assuming for a moment that our goal is setting the user flag on every active cell):

Triangulation<dim> triangulation;
...
typename Triangulation<dim>::active_cell_iterator
  cell = triangulation.begin_active(),
  endc = triangulation.end();
for (; cell!=endc; ++cell)
  cell->set_user_flag();

Using C++11's range-based for loops, this is now entirely equivalent to the following:

Triangulation<dim> triangulation;
...
for (auto cell : triangulation.active_cell_iterators())
  cell->set_user_flag();

To use this feature, you need a compiler that supports C++11.

Returns

The half open range [this->begin_active(), this->end())

Definition at line 10521 of file tria.cc.

cell_iterators_on_level() [2/3]

template<int dim, int spacedim>

IteratorRange< typename Triangulation< dim, spacedim >::cell_iterator > Triangulation< dim, spacedim >::cell_iterators_on_level

(

const unsigned int

level

)

const

Return an iterator range that contains all cells (active or not) that make up the given level of this triangulation. Such a range is useful to initialize range-based for loops as supported by C++11. See the example in the documentation of active_cell_iterators().

Parameters

[in]

level

A given level in the refinement hierarchy of this triangulation.

Returns

The half open range [this->begin(level), this->end(level))

Precondition

level must be less than this->n_levels().

Definition at line 10532 of file tria.cc.

active_cell_iterators_on_level() [2/3]

template<int dim, int spacedim>

IteratorRange< typename Triangulation< dim, spacedim >::active_cell_iterator > Triangulation< dim, spacedim >::active_cell_iterators_on_level

(

const unsigned int

level

)

const

Return an iterator range that contains all active cells that make up the given level of this triangulation. Such a range is useful to initialize range-based for loops as supported by C++11. See the example in the documentation of active_cell_iterators().

Parameters

[in]

level

A given level in the refinement hierarchy of this triangulation.

Returns

The half open range [this->begin_active(level), this->end(level))

Precondition

level must be less than this->n_levels().

Definition at line 10543 of file tria.cc.

cell_iterators() [3/3]

template<int dim, int spacedim>

IteratorRange< typename DoFHandler< dim, spacedim >::cell_iterator > DoFHandler< dim, spacedim >::cell_iterators

(

)

const

Return an iterator range that contains all cells (active or not) that make up this DoFHandler. Such a range is useful to initialize range- based for loops as supported by C++11. See the example in the documentation of active_cell_iterators().

Returns

The half open range [this->begin(), this->end())

Definition at line 1764 of file dof_handler.cc.

active_cell_iterators() [3/3]

template<int dim, int spacedim>

IteratorRange< typename DoFHandler< dim, spacedim >::active_cell_iterator > DoFHandler< dim, spacedim >::active_cell_iterators

(

)

const

Return an iterator range that contains all active cells that make up this DoFHandler. Such a range is useful to initialize range-based for loops as supported by C++11, see also C++11 standard.

Range-based for loops are useful in that they require much less code than traditional loops (see here for a discussion of how they work). An example is that without range-based for loops, one often writes code such as the following:

DoFHandler<dim> dof_handler;
...
typename DoFHandler<dim>::active_cell_iterator
  cell = dof_handler.begin_active(),
  endc = dof_handler.end();
for (; cell!=endc; ++cell)
  {
    fe_values.reinit (cell);
    ...do the local integration on 'cell'...;
  }

Using C++11's range-based for loops, this is now entirely equivalent to the following:

DoFHandler<dim> dof_handler;
...
for (auto cell : dof_handler.active_cell_iterators())
  {
    fe_values.reinit (cell);
    ...do the local integration on 'cell'...;
  }

To use this feature, you need a compiler that supports C++11.

Returns

The half open range [this->begin_active(), this->end())

Definition at line 1774 of file dof_handler.cc.

cell_iterators_on_level() [3/3]

template<int dim, int spacedim>

IteratorRange< typename DoFHandler< dim, spacedim >::cell_iterator > DoFHandler< dim, spacedim >::cell_iterators_on_level

(

const unsigned int

level

)

const

Return an iterator range that contains all cells (active or not) that make up the given level of this DoFHandler. Such a range is useful to initialize range-based for loops as supported by C++11. See the example in the documentation of active_cell_iterators().

Parameters

[in]

level

A given level in the refinement hierarchy of this triangulation.

Returns

The half open range [this->begin(level), this->end(level))

Precondition

level must be less than this->n_levels().

Definition at line 1785 of file dof_handler.cc.

active_cell_iterators_on_level() [3/3]

template<int dim, int spacedim>

IteratorRange< typename DoFHandler< dim, spacedim >::active_cell_iterator > DoFHandler< dim, spacedim >::active_cell_iterators_on_level

(

const unsigned int

level

)

const

Return an iterator range that contains all active cells that make up the given level of this DoFHandler. Such a range is useful to initialize range-based for loops as supported by C++11. See the example in the documentation of active_cell_iterators().

Parameters

[in]

level

A given level in the refinement hierarchy of this triangulation.

Returns

The half open range [this->begin_active(level), this->end(level))

Precondition

level must be less than this->n_levels().

Definition at line 1796 of file dof_handler.cc.