Reference documentation for deal.II version GIT relicensing-43-g3fc2fae7c3 2024-03-03 21:10:02+00:00
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Public Types | Public Member Functions | Protected Member Functions | Protected Attributes | List of all members
LinearIndexIterator< DerivedIterator, AccessorType > Class Template Reference

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

Inheritance diagram for LinearIndexIterator< DerivedIterator, AccessorType >:
Inheritance graph
[legend]

Public Types

using iterator_category = std::random_access_iterator_tag
 
using value_type = AccessorType
 
using difference_type = std::ptrdiff_t
 
using reference = const value_type &
 
using pointer = const value_type *
 
using size_type = typename value_type::size_type
 

Public Member Functions

DerivedIterator & operator= (const DerivedIterator &it)
 
DerivedIterator & operator++ ()
 
DerivedIterator operator++ (int)
 
DerivedIterator & operator-- ()
 
DerivedIterator operator-- (int)
 
DerivedIterator operator+ (const difference_type n) const
 
DerivedIterator operator- (const difference_type n) const
 
DerivedIterator & operator+= (const difference_type n)
 
DerivedIterator & operator-= (const difference_type n)
 
difference_type operator- (const DerivedIterator &p) const
 
reference operator* () const
 
pointer operator-> () const
 
template<typename OtherIterator >
std::enable_if_t< std::is_convertible_v< OtherIterator, DerivedIterator >, booloperator== (const OtherIterator &right) const
 
template<typename OtherIterator >
std::enable_if_t< std::is_convertible_v< OtherIterator, DerivedIterator >, booloperator!= (const OtherIterator &right) const
 
bool operator<= (const DerivedIterator &) const
 
bool operator>= (const DerivedIterator &) const
 
bool operator< (const DerivedIterator &) const
 
bool operator> (const DerivedIterator &) const
 

Protected Member Functions

 LinearIndexIterator ()=default
 
 LinearIndexIterator (const AccessorType accessor)
 

Protected Attributes

AccessorType accessor
 

Detailed Description

template<typename DerivedIterator, typename AccessorType>
class LinearIndexIterator< DerivedIterator, AccessorType >

Many classes in deal.II, such as FullMatrix, TransposeTable, and SparseMatrix, store their data in contiguous buffers (though the interpretation of what the elements of these buffers represent can, of course, be complex). For example, FullMatrix and TransposeTable store their data in row major and column major order respectively, whereas for SparseMatrix the mapping from buffer location to matrix entry \(\mathbf{A}(i, j)\) is more complicated. In any case, however, the contiguous arrangements of elements enables random access iteration.

LinearIndexIterator provides most of the functionality needed to write iterators for these classes. LinearIndexIterator is essentially a simplified version of boost::iterator_facade that assumes AccessorType provides certain members (documented below) that completely describe the state of the iterator. The intended use of this class is for containers to define their own accessor classes and then use the curiously recurring template pattern (CRTP) technique to define their iterators. For example, here is a container that uses LinearIndexIterator to define its own iterator classes:

template <typename T>
class Container
{
protected:
// forward declaration for friendship
template <bool Constness>
class Iterator;
template <bool Constness>
class Accessor
{
public:
// const iterators store a const pointer
using container_pointer_type
= std::conditional_t<Constness,
const Container<T>*,
Container<T>*>;
// This alias is assumed to exist.
using size_type = std::size_t;
// constructor.
Accessor(const container_pointer_type container,
const std::ptrdiff_t index);
// constructor.
Accessor();
// get a constant reference to the current value.
const T& value() const;
protected:
container_pointer_type container;
std::ptrdiff_t linear_index;
// LinearIndexIterator needs access to linear_index and container.
friend class LinearIndexIterator<Iterator<Constness>,
Accessor<Constness>>;
};
template <bool Constness>
class Iterator : public LinearIndexIterator<Iterator<Constness>,
Accessor<Constness>>
{
// Constructor.
Iterator(Container<T> * const container, const std::ptrdiff_t index);
// implement additional constructors here, but all state should be
// contained in the Accessor, which is a member of the base class.
};
public:
using size_type = std::size_t;
using const_iterator = Iterator<true>;
using iterator = Iterator<false>;
iterator begin ();
iterator end ();
const_iterator begin () const;
const_iterator end () const;
};
typename value_type::size_type size_type
types::global_dof_index size_type
const Iterator const std_cxx20::type_identity_t< Iterator > & end
Definition parallel.h:610
const Iterator & begin
Definition parallel.h:609
Template Parameters
DerivedIteratorAs shown in the example above, concrete iterator classes should use this class with the CRTP technique: this provides the boiler-plate comparison and arithmetic operators for iterators. This is necessary for, e.g., LinearIndexIterator::operator++() to return the correct type.
AccessorTypeLinearIndexIterator assumes that the AccessorType template parameter has the following members which completely describe the current state of the iterator:
  1. A pointer named container to the original container (e.g., the relevant SparseMatrix). This should be a const pointer for const iterators.
  2. An array index named linear_index that stores the current position in the container's storage buffer. linear_index does not need to be an integer: it could be a class type (convertible to the correct index type of the container) that implements operator+=, operator<, and operator==. For example, one could implement a strided iterator by implementing operator+= and operator- with multiplicative factors.
In addition, AccessorType should declare the relevant LinearIndexIterator instantiation to be a friend and define a size_type type.
Note
TransposeTable uses this template to implement its iterators.

Definition at line 138 of file linear_index_iterator.h.

Member Typedef Documentation

◆ iterator_category

template<typename DerivedIterator , typename AccessorType >
using LinearIndexIterator< DerivedIterator, AccessorType >::iterator_category = std::random_access_iterator_tag

Iterator category.

Definition at line 147 of file linear_index_iterator.h.

◆ value_type

template<typename DerivedIterator , typename AccessorType >
using LinearIndexIterator< DerivedIterator, AccessorType >::value_type = AccessorType

An alias for the type you get when you dereference an iterator of the current kind.

Definition at line 154 of file linear_index_iterator.h.

◆ difference_type

template<typename DerivedIterator , typename AccessorType >
using LinearIndexIterator< DerivedIterator, AccessorType >::difference_type = std::ptrdiff_t

Difference type.

Definition at line 159 of file linear_index_iterator.h.

◆ reference

template<typename DerivedIterator , typename AccessorType >
using LinearIndexIterator< DerivedIterator, AccessorType >::reference = const value_type &

Reference type.

Definition at line 164 of file linear_index_iterator.h.

◆ pointer

template<typename DerivedIterator , typename AccessorType >
using LinearIndexIterator< DerivedIterator, AccessorType >::pointer = const value_type *

Pointer type.

Definition at line 169 of file linear_index_iterator.h.

◆ size_type

template<typename DerivedIterator , typename AccessorType >
using LinearIndexIterator< DerivedIterator, AccessorType >::size_type = typename value_type::size_type

Size type used by the underlying container.

Definition at line 174 of file linear_index_iterator.h.

Constructor & Destructor Documentation

◆ LinearIndexIterator() [1/2]

template<typename DerivedIterator , typename AccessorType >
LinearIndexIterator< DerivedIterator, AccessorType >::LinearIndexIterator ( )
protecteddefault

◆ LinearIndexIterator() [2/2]

template<typename DerivedIterator , typename AccessorType >
LinearIndexIterator< DerivedIterator, AccessorType >::LinearIndexIterator ( const AccessorType  accessor)
inlineprotected

Constructor that copies an accessor.

Definition at line 503 of file linear_index_iterator.h.

Member Function Documentation

◆ operator=()

template<typename DerivedIterator , typename AccessorType >
DerivedIterator & LinearIndexIterator< DerivedIterator, AccessorType >::operator= ( const DerivedIterator &  it)
inline

Copy operator.

Definition at line 332 of file linear_index_iterator.h.

◆ operator++() [1/2]

template<typename DerivedIterator , typename AccessorType >
DerivedIterator & LinearIndexIterator< DerivedIterator, AccessorType >::operator++ ( )
inline

Prefix increment.

Definition at line 344 of file linear_index_iterator.h.

◆ operator++() [2/2]

template<typename DerivedIterator , typename AccessorType >
DerivedIterator LinearIndexIterator< DerivedIterator, AccessorType >::operator++ ( int  )
inline

Postfix increment.

Definition at line 353 of file linear_index_iterator.h.

◆ operator--() [1/2]

template<typename DerivedIterator , typename AccessorType >
DerivedIterator & LinearIndexIterator< DerivedIterator, AccessorType >::operator-- ( )
inline

Prefix decrement.

Definition at line 364 of file linear_index_iterator.h.

◆ operator--() [2/2]

template<typename DerivedIterator , typename AccessorType >
DerivedIterator LinearIndexIterator< DerivedIterator, AccessorType >::operator-- ( int  )
inline

Postfix decrement.

Definition at line 373 of file linear_index_iterator.h.

◆ operator+()

template<typename DerivedIterator , typename AccessorType >
DerivedIterator LinearIndexIterator< DerivedIterator, AccessorType >::operator+ ( const difference_type  n) const
inline

Return an iterator that is n entries ahead of the current one.

Definition at line 384 of file linear_index_iterator.h.

◆ operator-() [1/2]

template<typename DerivedIterator , typename AccessorType >
DerivedIterator LinearIndexIterator< DerivedIterator, AccessorType >::operator- ( const difference_type  n) const
inline

Return an iterator that is n entries behind the current one.

Definition at line 396 of file linear_index_iterator.h.

◆ operator+=()

template<typename DerivedIterator , typename AccessorType >
DerivedIterator & LinearIndexIterator< DerivedIterator, AccessorType >::operator+= ( const difference_type  n)
inline

Increment the iterator position by n.

Definition at line 408 of file linear_index_iterator.h.

◆ operator-=()

template<typename DerivedIterator , typename AccessorType >
DerivedIterator & LinearIndexIterator< DerivedIterator, AccessorType >::operator-= ( const difference_type  n)
inline

Decrement the iterator position by n.

Definition at line 419 of file linear_index_iterator.h.

◆ operator-() [2/2]

template<typename DerivedIterator , typename AccessorType >
LinearIndexIterator< DerivedIterator, AccessorType >::difference_type LinearIndexIterator< DerivedIterator, AccessorType >::operator- ( const DerivedIterator &  p) const
inline

Return the distance between the current iterator and the argument. The distance is given by how many times one has to apply operator++() to the current iterator to get the argument (for a positive return value), or operator--() (for a negative return value).

Definition at line 430 of file linear_index_iterator.h.

◆ operator*()

template<typename DerivedIterator , typename AccessorType >
LinearIndexIterator< DerivedIterator, AccessorType >::reference LinearIndexIterator< DerivedIterator, AccessorType >::operator* ( ) const
inline

Dereferencing operator.

Definition at line 443 of file linear_index_iterator.h.

◆ operator->()

template<typename DerivedIterator , typename AccessorType >
LinearIndexIterator< DerivedIterator, AccessorType >::pointer LinearIndexIterator< DerivedIterator, AccessorType >::operator-> ( ) const
inline

Dereferencing operator.

Definition at line 452 of file linear_index_iterator.h.

◆ operator==()

template<typename DerivedIterator , typename AccessorType >
template<typename OtherIterator >
std::enable_if_t< std::is_convertible_v< OtherIterator, DerivedIterator >, bool > LinearIndexIterator< DerivedIterator, AccessorType >::operator== ( const OtherIterator &  right) const
inline

Comparison operator. Returns true if both iterators point to the same entry in the same container.

Definition at line 257 of file linear_index_iterator.h.

◆ operator!=()

template<typename DerivedIterator , typename AccessorType >
template<typename OtherIterator >
std::enable_if_t< std::is_convertible_v< OtherIterator, DerivedIterator >, bool > LinearIndexIterator< DerivedIterator, AccessorType >::operator!= ( const OtherIterator &  right) const
inline

Opposite of operator==().

Definition at line 268 of file linear_index_iterator.h.

◆ operator<=()

template<typename DerivedIterator , typename AccessorType >
bool LinearIndexIterator< DerivedIterator, AccessorType >::operator<= ( const DerivedIterator &  other) const
inline

Comparison operator: uses the same ordering as operator<(), but also checks for equality.

This function is only valid if both iterators point into the same container.

Definition at line 460 of file linear_index_iterator.h.

◆ operator>=()

template<typename DerivedIterator , typename AccessorType >
bool LinearIndexIterator< DerivedIterator, AccessorType >::operator>= ( const DerivedIterator &  other) const
inline

Comparison operator: uses the same ordering as operator>(), but also checks for equality.

This function is only valid if both iterators point into the same container.

Definition at line 471 of file linear_index_iterator.h.

◆ operator<()

template<typename DerivedIterator , typename AccessorType >
bool LinearIndexIterator< DerivedIterator, AccessorType >::operator< ( const DerivedIterator &  other) const
inline

Comparison operator. Result is true if either the first row number is smaller or if the row numbers are equal and the first index is smaller.

This function is only valid if both iterators point into the same container.

Definition at line 480 of file linear_index_iterator.h.

◆ operator>()

template<typename DerivedIterator , typename AccessorType >
bool LinearIndexIterator< DerivedIterator, AccessorType >::operator> ( const DerivedIterator &  other) const
inline

Comparison operator. Works in the same way as operator<(), just the other way round.

Definition at line 494 of file linear_index_iterator.h.

Member Data Documentation

◆ accessor

template<typename DerivedIterator , typename AccessorType >
AccessorType LinearIndexIterator< DerivedIterator, AccessorType >::accessor
protected

Store an object of the accessor class.

Definition at line 325 of file linear_index_iterator.h.


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