Reference documentation for deal.II version Git b85d307 2018-08-20 17:45:16 -0600
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 >:
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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
 
bool operator== (const DerivedIterator &) const
 
bool operator!= (const DerivedIterator &) 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<class DerivedIterator, class 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
= typename std::conditional<Constness,
const Container<T>*,
Container<T>*>::type;
// 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;
};
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.
Author
David Wells, 2018

Definition at line 141 of file linear_index_iterator.h.

Member Typedef Documentation

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

Iterator category.

Definition at line 147 of file linear_index_iterator.h.

template<class DerivedIterator, class 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 153 of file linear_index_iterator.h.

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

Difference type.

Definition at line 158 of file linear_index_iterator.h.

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

Reference type.

Definition at line 163 of file linear_index_iterator.h.

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

Pointer type.

Definition at line 168 of file linear_index_iterator.h.

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

Size type used by the underlying container.

Definition at line 173 of file linear_index_iterator.h.

Constructor & Destructor Documentation

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

The inheriting class should have a default constructor.

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

Constructor that copies an accessor.

Definition at line 513 of file linear_index_iterator.h.

Member Function Documentation

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

Copy operator.

Definition at line 321 of file linear_index_iterator.h.

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

Prefix increment.

Definition at line 332 of file linear_index_iterator.h.

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

Postfix increment.

Definition at line 341 of file linear_index_iterator.h.

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

Prefix decrement.

Definition at line 352 of file linear_index_iterator.h.

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

Postfix decrement.

Definition at line 361 of file linear_index_iterator.h.

template<class DerivedIterator , class 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 373 of file linear_index_iterator.h.

template<class DerivedIterator , class 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 385 of file linear_index_iterator.h.

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

Increment the iterator position by n.

Definition at line 397 of file linear_index_iterator.h.

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

Decrement the iterator position by n.

Definition at line 408 of file linear_index_iterator.h.

template<class DerivedIterator, class 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 419 of file linear_index_iterator.h.

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

Dereferencing operator.

Definition at line 431 of file linear_index_iterator.h.

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

Dereferencing operator.

Definition at line 440 of file linear_index_iterator.h.

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

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

Definition at line 450 of file linear_index_iterator.h.

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

Inverse of operator==().

Definition at line 462 of file linear_index_iterator.h.

template<class DerivedIterator, class 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 472 of file linear_index_iterator.h.

template<class DerivedIterator, class 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 482 of file linear_index_iterator.h.

template<class DerivedIterator, class 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 492 of file linear_index_iterator.h.

template<class DerivedIterator, class 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 505 of file linear_index_iterator.h.

Member Data Documentation

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

Store an object of the accessor class.

Definition at line 313 of file linear_index_iterator.h.


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