DGtal::IteratorCompletion< TDerived > Class Template Reference

Aim: Class that uses CRTP to add reverse iterators and ranges to a derived class. More...

#include <DGtal/base/IteratorCompletion.h>

Public Types
typedef IteratorCompletionTraits< TDerived >::Iterator	Iterator
	Mutable iterator type. More...
typedef IteratorCompletionTraits< TDerived >::ConstIterator	ConstIterator
	Constant iterator type. More...
typedef IteratorCompletionTraits< TDerived >::DistanceFunctor	DistanceFunctor
	Type of the functor calculating the distance between iterators. More...
typedef boost::reverse_iterator< Iterator >	ReverseIterator
	Mutable reverse iterator type. More...
typedef boost::reverse_iterator< ConstIterator >	ConstReverseIterator
	Constant reverse iterator type. More...
typedef SimpleRandomAccessRangeFromPoint< ConstIterator, Iterator, DistanceFunctor >	Range
	Mutable range type. More...
typedef SimpleRandomAccessConstRangeFromPoint< ConstIterator, DistanceFunctor >	ConstRange
	Constant range type. More...
typedef std::ptrdiff_t	Difference
	Type of the distance between two iterators. More...

Public Member Functions
ReverseIterator	rbegin ()
ConstReverseIterator	rbegin () const
ConstReverseIterator	crbegin () const
ReverseIterator	rend ()
ConstReverseIterator	rend () const
ConstReverseIterator	crend () const
Range	range ()
ConstRange	constRange () const

Protected Member Functions
	~IteratorCompletion ()
	Protected destructor to avoid memory leak. More...

Detailed Description

template<typename TDerived>
class DGtal::IteratorCompletion< TDerived >

Aim: Class that uses CRTP to add reverse iterators and ranges to a derived class.

Description of template class 'IteratorCompletionTraits'

This class adds new iterators to a given class if it provides a minimal interface for random-access iterators related to points.

More precisely, it provides:

• reverse mutable and constant iterators,
• mutable and constant ranges,
• constant normal and reverse iterators from C++11 if the class provides cbegin and cend methods.

Each derived class of IteratorCompletion must specialize IteratorCompletionTraits in order to provide enough informations on his iterators, especially a distance functor between a given point and the begin iterator.

Template Parameters

TDerived

Type of the derived class (CRTP).

The following snippets illustrate how to use it to easily build a concepts::CImage model from a C-style array (better use ArrayImageAdapter for that purpose).

After common includes:

#include <new>
#include <cstddef>
#include <algorithm>
#include <iostream>
 
#include <DGtal/base/Common.h>
#include <DGtal/base/IteratorCompletion.h>
#include <DGtal/kernel/domains/HyperRectDomain.h>
#include <DGtal/kernel/domains/Linearizer.h>
#include <DGtal/kernel/SpaceND.h>
#include <DGtal/images/CImage.h>

we start with the head of our class, including typedefs, constructor and destructor:

 
// A minimal image from a C-style array with reverse-iterators and ranges.
template < typename T, DGtal::Dimension N >
class MyImage
  : public DGtal::IteratorCompletion< MyImage<T, N> >   // CRTP
{
public:
 
  // Typedefs
  typedef MyImage<T, N>   Self;
  typedef typename DGtal::IteratorCompletionTraits<Self>::Iterator       Iterator; // to be coherent with the traits that use IteratorCompletion
  typedef typename DGtal::IteratorCompletionTraits<Self>::ConstIterator  ConstIterator; // same ...
 
  typedef T                               Value;  // The image values type
  typedef DGtal::SpaceND<N>               Space;  // The image space type
  typedef DGtal::HyperRectDomain<Space>   Domain; // The image domain type
  typedef typename Space::Point           Point;  // The associated point type
  typedef DGtal::Linearizer<Domain, DGtal::ColMajorStorage>    Linearizer; 
  
  // Contructor
  MyImage( Domain const& aDomain = Domain() )
    : myDomain(aDomain), myData( new T[ myDomain.size() ] )
    {}
 
  // Destructor
  ~MyImage()
    {
      delete[] myData;
    }
 

As you can see, the MyImage class inherits from IteratorCompletion templated with his own type (CRTP). The public inheritance is necessary is order to make visible the methods and typedefs provided by IteratorCompletion.

Then, we add the basic interface needed for images:

 
  // Unary Functor
  Value operator() ( Point const& aPoint ) const
    {
      return myData[ Linearizer::getIndex(aPoint, myDomain) ];
    }
 
  // Getter
  Value getValue( Point const& aPoint ) const
    {
      return operator()(aPoint);
    }
 
  // Setter
  void setValue( Point const& aPoint, Value const& aValue )
    {
      myData[ Linearizer::getIndex(aPoint, myDomain) ] = aValue;
    }
 
  // Returns the associated domain
  Domain const& domain() const
    {
      return myDomain;
    }
 
  // Assignability (needed for CImage concept)
  Self& operator= ( Self const& other )
    {
      if ( this != &other )
        {
          myDomain = other.domain();
          delete[] myData;
          myData = new Value[ myDomain.size() ];
          std::copy( other.begin(), other.end(), begin() );
        }
 
      return *this;
    }
 

and the minimal iterator accessors:

 
// Begin mutable iterator
  Iterator begin()
    {
      return myData;
    }
 
  // Begin constant iterator
  ConstIterator begin() const
    {
      return myData;
    }
 
  // End mutable iterator
  Iterator end()
    {
      return myData + myDomain.size();
    }
 
  // End constant iterator
  ConstIterator end() const
    {
      return myData + myDomain.size();
    }
  

The class is finally closed with the private members:

private:
  Domain myDomain;
  T* myData;
 
};

A specialization of IteratorCompletionTraits is needed in order to provide IteratorCompletion with the Iterator and ConstIterator type, and a DistanceFunctor that returns the distance from the begin iterator to a given point (see SimpleRandomAccessRangeFromPoint and SimpleRandomAccessConstRangeFromPoint):

namespace DGtal
{
  // Specialization of IteratorCompletionTraits for MyVector
  template < typename T, Dimension N >
  class IteratorCompletionTraits< MyImage<T, N> >
    {
    public:
      typedef MyImage<T, N> Self;
      typedef T*            Iterator;
      typedef T const*      ConstIterator;
      
      class DistanceFunctor
        {
        public:
          typedef typename Self::Domain     Domain;
          typedef typename Self::Point      Point;
          typedef typename Self::Difference Difference;
 
          DistanceFunctor( Self const* aVector )
            : myDomain(aVector->domain())
            {}
 
          Difference operator() ( Point const& aPoint ) const
            {
              return Self::Linearizer::getIndex( aPoint, myDomain );
            }
 
        private:
          Domain myDomain;
        };
      
    };
}

We have now a concepts::CImage model that can be used like any image:

  using namespace std;
 
  // Typedefs
  typedef MyImage<double, 2>  My2DImage;
  typedef My2DImage::Value    Value;
  typedef My2DImage::Domain   Domain;
  typedef My2DImage::Point    Point;
  
  // Checks CImage concept
  BOOST_CONCEPT_ASSERT( (DGtal::concepts::CImage<My2DImage>) );
 
  // Construction
  My2DImage image( Domain( Point(0,0), Point(2,3) ) );
 
  // Filling
  Value i = 0;
  for ( My2DImage::Iterator it = image.begin(), it_end = image.end() ; it != it_end; ++it )
    {
      *it = ++i;
    }
 
  // Modifying a value
  image.setValue( Point(1,1), -1 );
 
  // Forward reading using range
  My2DImage::ConstRange range = image.constRange();
  copy( range.begin(), range.end(), ostream_iterator<Value>( cout, " " ) );
  cout << endl;
 
  // Backward reading using reverse iterators
  copy( image.rbegin(), image.rend(), ostream_iterator<Value>( cout, " " ) );
  cout << endl;
 

See also

ArrayImageAdapter.h

exampleIteratorCompletion.cpp

Definition at line 116 of file IteratorCompletion.h.

Member Typedef Documentation

ConstIterator

template<typename TDerived >

typedef IteratorCompletionTraits<TDerived>::ConstIterator DGtal::IteratorCompletion< TDerived >::ConstIterator

Constant iterator type.

Definition at line 121 of file IteratorCompletion.h.

ConstRange

template<typename TDerived >

typedef SimpleRandomAccessConstRangeFromPoint< ConstIterator, DistanceFunctor > DGtal::IteratorCompletion< TDerived >::ConstRange

Constant range type.

Definition at line 127 of file IteratorCompletion.h.

ConstReverseIterator

template<typename TDerived >

typedef boost::reverse_iterator<ConstIterator> DGtal::IteratorCompletion< TDerived >::ConstReverseIterator

Constant reverse iterator type.

Definition at line 125 of file IteratorCompletion.h.

Difference

template<typename TDerived >

typedef std::ptrdiff_t DGtal::IteratorCompletion< TDerived >::Difference

Type of the distance between two iterators.

Definition at line 128 of file IteratorCompletion.h.

DistanceFunctor

template<typename TDerived >

typedef IteratorCompletionTraits<TDerived>::DistanceFunctor DGtal::IteratorCompletion< TDerived >::DistanceFunctor

Type of the functor calculating the distance between iterators.

Definition at line 122 of file IteratorCompletion.h.

Iterator

template<typename TDerived >

typedef IteratorCompletionTraits<TDerived>::Iterator DGtal::IteratorCompletion< TDerived >::Iterator

Mutable iterator type.

Definition at line 120 of file IteratorCompletion.h.

Range

template<typename TDerived >

typedef SimpleRandomAccessRangeFromPoint< ConstIterator, Iterator, DistanceFunctor > DGtal::IteratorCompletion< TDerived >::Range

Mutable range type.

Definition at line 126 of file IteratorCompletion.h.

ReverseIterator

template<typename TDerived >

typedef boost::reverse_iterator<Iterator> DGtal::IteratorCompletion< TDerived >::ReverseIterator

Mutable reverse iterator type.

Definition at line 124 of file IteratorCompletion.h.

Constructor & Destructor Documentation

~IteratorCompletion()

template<typename TDerived >

DGtal::IteratorCompletion< TDerived >::~IteratorCompletion ( )

inlineprotected

Protected destructor to avoid memory leak.

Definition at line 224 of file IteratorCompletion.h.

        {}

Member Function Documentation

constRange()

template<typename TDerived >

ConstRange DGtal::IteratorCompletion< TDerived >::constRange ( ) const

inline

Returns

a constant range over the derived class values.

Warning

the derived class must have begin() and end() methods that return constant random-access iterators.

In addition, the class must provide a distance functor to a point.

Definition at line 211 of file IteratorCompletion.h.

        {
          TDerived const* const derived = static_cast<TDerived const*>(this);
          return ConstRange(
              derived->begin(),
              derived->end(),
              typename IteratorCompletionTraits<TDerived>::DistanceFunctor( derived )
          );
        }

crbegin()

template<typename TDerived >

ConstReverseIterator DGtal::IteratorCompletion< TDerived >::crbegin ( ) const

inline

Returns

a constant reverse-iterator pointing to the last value (C++11).

Warning

the derived class must have a cend() method that returns a constant bidirectional iterator.

Definition at line 154 of file IteratorCompletion.h.

        {
          return ConstReverseIterator( static_cast<TDerived*>(this)->cend() );
        }

crend()

template<typename TDerived >

ConstReverseIterator DGtal::IteratorCompletion< TDerived >::crend ( ) const

inline

Returns

a constant reverse-iterator pointing before the first value (C++11).

Warning

the derived class must have a cbegin() method that returns a constant bidirectional iterator.

Definition at line 184 of file IteratorCompletion.h.

        {
          return ConstReverseIterator( static_cast<TDerived*>(this)->cbegin() );
        }

range()

template<typename TDerived >

Range DGtal::IteratorCompletion< TDerived >::range ( )

inline

Returns

a mutable range over the derived class values.

Warning

the derived class must have begin() and end() methods that return mutable random-access iterators.

In addition, the class must provide a distance functor to a point.

Definition at line 195 of file IteratorCompletion.h.

        {
          TDerived* const derived = static_cast<TDerived*>(this);
          return Range(
              derived->begin(),
              derived->end(),
              typename IteratorCompletionTraits<TDerived>::DistanceFunctor( derived )
          );
        }

rbegin() [1/2]

template<typename TDerived >

ReverseIterator DGtal::IteratorCompletion< TDerived >::rbegin ( )

inline

Returns

a mutable reverse-iterator pointing to the last value.

Warning

the derived class must have a end() method that returns a mutable bidirectional iterator.

Definition at line 134 of file IteratorCompletion.h.

        {
          return ReverseIterator( static_cast<TDerived*>(this)->end() );
        }

rbegin() [2/2]

template<typename TDerived >

ConstReverseIterator DGtal::IteratorCompletion< TDerived >::rbegin ( ) const

inline

Returns

a constant reverse-iterator pointing to the last value.

Warning

the derived class must have a end() method that returns a constant bidirectional iterator.

Definition at line 144 of file IteratorCompletion.h.

        {
          return ConstReverseIterator( static_cast<TDerived*>(this)->end() );
        }

rend() [1/2]

template<typename TDerived >

ReverseIterator DGtal::IteratorCompletion< TDerived >::rend ( )

inline

Returns

a mutable reverse-iterator pointing before the first value.

Warning

the derived class must have a begin() method that returns a mutable bidirectional iterator.

Definition at line 164 of file IteratorCompletion.h.

        {
          return ReverseIterator( static_cast<TDerived*>(this)->begin() );
        }

rend() [2/2]

template<typename TDerived >

ConstReverseIterator DGtal::IteratorCompletion< TDerived >::rend ( ) const

inline

Returns

a constant reverse-iterator pointing before the first value.

Warning

the derived class must have a begin() method that returns a constant bidirectional iterator.

Definition at line 174 of file IteratorCompletion.h.

        {
          return ConstReverseIterator( static_cast<TDerived*>(this)->begin() );
        }

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

• IteratorCompletion.h