LinearIndexIterator< DerivedIterator, AccessorType > Class Template Reference

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

Inheritance diagram for LinearIndexIterator< DerivedIterator, AccessorType >:

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

DerivedIterator

As 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.

AccessorType

LinearIndexIterator assumes that the AccessorType template parameter has the following members which completely describe the current state of the iterator: A pointer named container to the original container (e.g., the relevant SparseMatrix). This should be a const pointer for const iterators. 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

iterator_category

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.

value_type

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.

difference_type

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.

reference

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.

pointer

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.

size_type

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

LinearIndexIterator() [1/2]

template<class DerivedIterator , class AccessorType >

LinearIndexIterator< DerivedIterator, AccessorType >::LinearIndexIterator ( )

protecteddefault

LinearIndexIterator() [2/2]

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

operator=()

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.

operator++() [1/2]

template<class DerivedIterator , class AccessorType >

DerivedIterator & LinearIndexIterator< DerivedIterator, AccessorType >::operator++

inline

Prefix increment.

Definition at line 332 of file linear_index_iterator.h.

operator++() [2/2]

template<class DerivedIterator , class AccessorType >

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

inline

Postfix increment.

Definition at line 341 of file linear_index_iterator.h.

operator--() [1/2]

template<class DerivedIterator , class AccessorType >

DerivedIterator & LinearIndexIterator< DerivedIterator, AccessorType >::operator--

inline

Prefix decrement.

Definition at line 352 of file linear_index_iterator.h.

operator--() [2/2]

template<class DerivedIterator , class AccessorType >

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

inline

Postfix decrement.

Definition at line 361 of file linear_index_iterator.h.

operator+()

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.

operator-() [1/2]

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.

operator+=()

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.

operator-=()

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.

operator-() [2/2]

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.

operator*()

template<class DerivedIterator , class AccessorType >

LinearIndexIterator< DerivedIterator, AccessorType >::reference LinearIndexIterator< DerivedIterator, AccessorType >::operator*

inline

Dereferencing operator.

Definition at line 431 of file linear_index_iterator.h.

operator->()

template<class DerivedIterator , class AccessorType >

LinearIndexIterator< DerivedIterator, AccessorType >::pointer LinearIndexIterator< DerivedIterator, AccessorType >::operator->

inline

Dereferencing operator.

Definition at line 440 of file linear_index_iterator.h.

operator==()

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.

operator!=()

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.

operator<=()

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.

operator>=()

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.

operator<()

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.

operator>()

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

accessor

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.

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

• include/deal.II/base/linear_index_iterator.h