iterator(3C++std)

advance , back_insert_iterator , back_inserter , bidirectional_iterator_tag , distance , forward_iterator_tag , front_insert_iterator , front_inserter , input_iterator_tag , insert_iterator , inserter , istream_iterator , istreambuf_iterator , iterator , iterator_traits , operator!= , operator== , operator< , operator<= , operator> , operator>= , operator+ , operator- , ostream_iterator , ostreambuf_iterator , output_iterator_tag , random_access_iterator_tag , reverse_iterator - defines several templates that help define and manipulate iterators (standard template library)

Synopsis

   namespace std {
   struct input_iterator_tag;
   struct output_iterator_tag;
   struct forward_iterator_tag;
   struct bidirectional_iterator_tag;
   struct random_access_iterator_tag;

           // TEMPLATE CLASSES
   template<class C, class T, class Dist,
       class Pt, class Rt>
       struct iterator;
   template<class It>
       struct iterator_traits;
   template<class T>
       struct iterator_traits<T *>
   template<class RanIt>
       class reverse_iterator;
   template<class Cont>
       class back_insert_iterator;
   template<class Cont>
       class front_insert_iterator;
   template<class Cont>
       class insert_iterator;
   template<class U, class E, class T, class Dist>
       class istream_iterator;
   template<class U, class E, class T>
       class ostream_iterator;
   template<class E, class T>
       class istreambuf_iterator;
   template<class E, class T>
       class ostreambuf_iterator;

           // TEMPLATE FUNCTIONS
   template<class RanIt>
       bool operator==(
           const reverse_iterator<RanIt>& lhs,
           const reverse_iterator<RanIt>& rhs);
   template<class U, class E, class T, class Dist>
       bool operator==(
           const istream_iterator<U, E, T, Dist>& lhs,
           const istream_iterator<U, E, T, Dist>& rhs);
   template<class E, class T>
       bool operator==(
           const istreambuf_iterator<E, T>& lhs,
           const istreambuf_iterator<E, T>& rhs);
   template<class RanIt>
       bool operator!=(
           const reverse_iterator<RanIt>& lhs,
           const reverse_iterator<RanIt>& rhs);
   template<class U, class E, class T, class Dist>
       bool operator!=(
           const istream_iterator<U, E, T, Dist>& lhs,
           const istream_iterator<U, E, T, Dist>& rhs);
   template<class E, class T>
       bool operator!=(
           const istreambuf_iterator<E, T>& lhs,
           const istreambuf_iterator<E, T>& rhs);
   template<class RanIt>
       bool operator<(
           const reverse_iterator<RanIt>& lhs,
           const reverse_iterator<RanIt>& rhs);
   template<class RanIt>
       bool operator>(
           const reverse_iterator<RanIt>& lhs,
           const reverse_iterator<RanIt>& rhs);
   template<class RanIt>
       bool operator<=(
           const reverse_iterator<RanIt>& lhs,
           const reverse_iterator<RanIt>& rhs);
   template<class RanIt>
       bool operator>=(
           const reverse_iterator<RanIt>& lhs,
           const reverse_iterator<RanIt>& rhs);
   template<class RanIt>
       Dist operator-(
           const reverse_iterator<RanIt>& lhs,
           const reverse_iterator<RanIt>& rhs);
   template<class RanIt>
       reverse_iterator<RanIt> operator+(
           Dist n,
           const reverse_iterator<RanIt>& rhs);
   template<class Cont>
       back_insert_iterator<Cont> back_inserter(Cont& x);
   template<class Cont>
       front_insert_iterator<Cont> front_inserter(Cont& x);
   template<class Cont, class Iter>
       insert_iterator<Cont> inserter(Cont& x, Iter it);
   template<class InIt, class Dist>
       void advance(InIt& it, Dist n);
   template<class Init, class Dist>
       iterator_traits<InIt>::difference_type
           distance(InIt first, InIt last);
       };

Description

Include the STL standard header <iterator> to define a number of classes, template classes, and template functions that aid in the declaration and manipulation of iterators.

Iterator Conventions

The STL facilities make widespread use of iterators, to mediate between the various algorithms and the sequences upon which they act. For brevity in the remainder of this description, the name of an iterator type (or its prefix) indicates the category of iterators required for that type. In order of increasing power, the categories are summarized here as:

OutIt -- An output iterator X can only have a value V stored indirect on it, after which it must be incremented before the next store, as in (*X++ = V), (*X = V, ++X), or (*X = V, X++).
InIt -- An input iterator X can represent a singular value that indicates end-of-sequence. If an input iterator does not compare equal to its end-of-sequence value, it can have a value V accessed indirect on it any number of times, as in (V = *X). To progress to the next value, or end-of-sequence, you increment it, as in ++X, X++, or (V = *X++). Once you increment any copy of an input iterator, none of the other copies can safely be compared, dereferenced, or incremented thereafter.
FwdIt -- A forward iterator X can take the place of an output iterator (for writing) or an input iterator (for reading). You can, however, read (via V = *X) what you just wrote (via *X = V) through a forward iterator. And you can make multiple copies of a forward iterator, each of which can be dereferenced and incremented independently.
BidIt -- A bidirectional iterator X can take the place of a forward iterator. You can, however, also decrement a bidirectional iterator, as in --X, X--, or (V = *X--).
RanIt -- A random-access iterator X can take the place of a bidirectional iterator. You can also perform much the same integer arithmetic on a random-access iterator that you can on an object pointer. For N an integer object, you can write x[N], x + N, x - N, and N + X.

Note that an object pointer can take the place of a random-access iterator, or any other for that matter. All iterators can be assigned or copied. They are assumed to be lightweight objects and hence are often passed and returned by value, not by reference. Note also that none of the operations described above can throw an exception, at least when performed on a valid iterator.

The hierarchy of iterator categories can be summarize by showing three sequences. For write-only access to a sequence, you can use any of:

output iterator
    -> forward iterator
    -> bidirectional iterator
    -> random-access iterator

The right arrow means ``can be replaced by.'' So any algorithm that calls for an output iterator should work nicely with a forward iterator, for example, but not the other way around.

For read-only access to a sequence, you can use any of:

input iterator
    -> forward iterator
    -> bidirectional iterator
    -> random-access iterator

An input iterator is the weakest of all categories, in this case.

Finally, for read/write access to a sequence, you can use any of:

forward iterator
    -> bidirectional iterator
    -> random-access iterator

Remember that an object pointer can always serve as a random-access iterator. Hence, it can serve as any category of iterator, so long as it supports the proper read/write access to the sequence it designates.

An iterator It other than an object pointer must also define the member types required by the specialization iterator_traits<It>. Note that these requirements can be met by deriving It from the public base class iterator.

advance

   template<class InIt, class Dist>
       void advance(InIt& it, Dist n);

The template function effectively advances it by incrementing it n times. If InIt is a random-access iterator type, the function evaluates the expression it += n. Otherwise, it performs each increment by evaluating ++it. If InIt is an input or forward iterator type, n must not be negative.

back_insert_iterator

container_type , reference , back_insert_iterator , operator= , operator* , operator++ , operator++ , container

   template<class Cont>
       class back_insert_iterator
           : public iterator<output_iterator_tag,
               void, void, void, void> {
   public:
       typedef Cont container_type;
       typedef typename Cont::reference reference;
       explicit back_insert_iterator(Cont& x);
       back_insert_iterator&
           operator=(typename Cont::const_reference val);
       back_insert_iterator& operator*();
       back_insert_iterator& operator++();
       back_insert_iterator operator++(int);
   protected:
       Cont *container;
       };

The template class describes an output iterator object. It inserts elements into a container of type Cont, which it accesses via the protected pointer object it stores called container. The container must define:

the member type const_reference, which is the type of a constant reference to an element of the sequence controlled by the container
the member type reference, which is the type of a reference to an element of the sequence controlled by the container
the member type value_type, which is the type of an element of the sequence controlled by the container
the member function push_back(value_type c), which appends a new element with value c to the end of the sequence

back_insert_iterator::back_insert_iterator

   explicit back_insert_iterator(Cont& x);

The constructor initializes container with &x.

`back_insert_iterator::container_type`

   typedef Cont container_type;

The type is a synonym for the template parameter Cont.

back_insert_iterator::operator*

   back_insert_iterator& operator*();

The member function returns *this.

back_insert_iterator::operator++

   back_insert_iterator& operator++();
   back_insert_iterator operator++(int);

The member functions both return *this.

back_insert_iterator::operator=

   back_insert_iterator&
       operator=(typename Cont::const_reference val);

The member function evaluates container. push_back(val), then returns *this.

`back_insert_iterator::reference`

   typedef typename Cont::reference reference;

The type describes a reference to an element of the sequence controlled by the associated container.

back_inserter

   template<class Cont>
       back_insert_iterator<Cont> back_inserter(Cont& x);

The template function returns back_insert_iterator<Cont>(x).

bidirectional_iterator_tag

   struct bidirectional_iterator_tag
       : public forward_iterator_tag {
       };

The type is the same as iterator<It>::iterator_category when It describes an object that can serve as a bidirectional iterator.

distance

   template<class Init, class Dist>
       typename iterator_traits<InIt>::difference_type
           distance(InIt first, InIt last);

The template function sets a count n to zero. It then effectively advances first and increments n until first == last. If InIt is a random-access iterator type, the function evaluates the expression n += last - first. Otherwise, it performs each iterator increment by evaluating ++first. The function returns n.

forward_iterator_tag

   struct forward_iterator_tag
       : public input_iterator_tag {
       };

The type is the same as iterator<It>::iterator_category when It describes an object that can serve as a forward iterator.

front_insert_iterator

container_type , reference , front_insert_iterator , operator= , operator* , operator++ , operator++ , container

   template<class Cont>
       class front_insert_iterator
           : public iterator<output_iterator_tag,
               void, void, void, void> {
   public:
       typedef Cont container_type;
       typedef typename Cont::reference reference;
       explicit front_insert_iterator(Cont& x);
       front_insert_iterator&
           operator=(typename Cont::const_reference val);
       front_insert_iterator& operator*();
       front_insert_iterator& operator++();
       front_insert_iterator operator++(int);
   protected:
       Cont *container;
       };

the member type const_reference, which is the type of a constant reference to an element of the sequence controlled by the container
the member type reference, which is the type of a reference to an element of the sequence controlled by the container
the member type value_type, which is the type of an element of the sequence controlled by the container
the member function push_front(value_type c), which prepends a new element with value c to the beginning of the sequence

`front_insert_iterator::container_type`

   typedef Cont container_type;

The type is a synonym for the template parameter Cont.

front_insert_iterator::front_insert_iterator

   explicit front_insert_iterator(Cont& x);

The constructor initializes container with &x.

front_insert_iterator::operator*

   front_insert_iterator& operator*();

The member function returns *this.

front_insert_iterator::operator++

   front_insert_iterator& operator++();
   front_insert_iterator operator++(int);

The member functions both return *this.

front_insert_iterator::operator=

   front_insert_iterator&
       operator=(typename Cont::const_reference val);

The member function evaluates container. push_front(val), then returns *this.

`front_insert_iterator::reference`

   typedef typename Cont::reference reference;

The type describes a reference to an element of the sequence controlled by the associated container.

front_inserter

   template<class Cont>
       front_insert_iterator<Cont> front_inserter(Cont& x);

The template function returns front_insert_iterator<Cont>(x).

input_iterator_tag

   struct input_iterator_tag {
       };

The type is the same as iterator<It>::iterator_category when It describes an object that can serve as an input iterator.

insert_iterator

container_type , reference , insert_iterator , operator= , operator* , operator++ , operator++ , container , iter

   template<class Cont>
       class insert_iterator
           : public iterator<output_iterator_tag,
               void, void, void, void> {
   public:
       typedef Cont container_type;
       typedef typename Cont::reference reference;
       insert_iterator(Cont& x,
           typename Cont::iterator it);
       insert_iterator&
           operator=(typename Cont::const_reference val);
       insert_iterator& operator*();
       insert_iterator& operator++();
       insert_iterator& operator++(int);
   protected:
       Cont *container;
       typename Cont::iterator iter;
       };

the member type const_reference, which is the type of a constant reference to an element of the sequence controlled by the container
the member type iterator, which is the type of an iterator for the container
the member type reference, which is the type of a reference to an element of the sequence controlled by the container
the member type value_type, which is the type of an element of the sequence controlled by the container
the member function insert(iterator it, value_type c), which inserts a new element with value c immediately before the element designated by it in the controlled sequence, then returns an iterator that designates the inserted element

`insert_iterator::container_type`

   typedef Cont container_type;

The type is a synonym for the template parameter Cont.

insert_iterator::insert_iterator

   insert_iterator(Cont& x,
       typename Cont::iterator it);

The constructor initializes container with &x, and iter with it.

insert_iterator::operator*

   insert_iterator& operator*();

The member function returns *this.

insert_iterator::operator++

   insert_iterator& operator++();
   insert_iterator& operator++(int);

The member functions both return *this.

insert_iterator::operator=

   insert_iterator&
       operator=(typename Cont::const_reference val);

The member function evaluates iter = container. insert(iter, val), then returns *this.

`insert_iterator::reference`

   typedef typename Cont::reference reference;

The type describes a reference to an element of the sequence controlled by the associated container.

inserter

   template<class Cont, class Iter>
       insert_iterator<Cont> inserter(Cont& x, Iter it);

The template function returns insert_iterator<Cont>(x, it).

istream_iterator

char_type , traits_type , istream_type , istream_iterator , istream_iterator , operator* , operator-> , operator++ , operator++

   template<class U, class E = char,
       class T = char_traits>
       class Dist = ptrdiff_t>
       class istream_iterator
           : public iterator<input_iterator_tag,
               U, Dist, U *, U&> {
   public:
       typedef E char_type;
       typedef T traits_type;
       typedef basic_istream<E, T> istream_type;
       istream_iterator();
       istream_iterator(istream_type& is);
       const U& operator*() const;
       const U *operator->() const;
       istream_iterator<U, E, T, Dist>& operator++();
       istream_iterator<U, E, T, Dist> operator++(int);
       };

The template class describes an input iterator object. It extracts objects of class U from an input stream, which it accesses via an object it stores, of type pointer to basic_istream<E, T>. After constructing or incrementing an object of class istream_iterator with a non-null stored pointer, the object attempts to extract and store an object of type U from the associated input stream. If the extraction fails, the object effectively replaces the stored pointer with a null pointer (thus making an end-of-sequence indicator).

istream_iterator::char_type

   typedef E char_type;

The type is a synonym for the template parameter E.

istream_iterator::istream_iterator

   istream_iterator();
   istream_iterator(istream_type& is);

The first constructor initializes the input stream pointer with a null pointer. The second constructor initializes the input stream pointer with &is, then attempts to extract and store an object of type U.

istream_iterator::istream_type

   typedef basic_istream<E, T> istream_type;

The type is a synonym for basic_istream<E, T>.

istream_iterator::operator*

   const U& operator*() const;

The operator returns the stored object of type U.

`istream_iterator::operator->`

   const U *operator->() const;

The operator returns &**this.

istream_iterator::operator++

   istream_iterator<U, E, T, Dist>& operator++();
   istream_iterator<U, E, T, Dist> operator++(int);

The first operator attempts to extract and store an object of type U from the associated input stream. The second operator makes a copy of the object, increments the object, then returns the copy.

istream_iterator::traits_type

   typedef T traits_type;

The type is a synonym for the template parameter T.

istreambuf_iterator

char_type ,traits_type ,int_type ,streambuf_type ,istream_type ,istreambuf_iterator ,istreambuf_iterator ,operator* ,operator-> ,operator++ ,operator++ ,equal

   template<class E, class T = char_traits<E> >
       class istreambuf_iterator
           : public iterator<input_iterator_tag,
               E, typename T::off_type, E *, E&> {
   public:
       typedef E char_type;
       typedef T traits_type;
       typedef typename T::int_type int_type;
       typedef basic_streambuf<E, T> streambuf_type;
       typedef basic_istream<E, T> istream_type;
       istreambuf_iterator(streambuf_type *sb = 0) throw();
       istreambuf_iterator(istream_type& is) throw();
       const E& operator*() const;
       const E *operator->();
       istreambuf_iterator& operator++();
       istreambuf_iterator operator++(int);
       bool equal(const istreambuf_iterator& rhs) const;
       };

The template class describes an input iterator object. It extracts elements of class E from an input stream buffer, which it accesses via an object it stores, of type pointer to basic_streambuf<E, T>. After constructing or incrementing an object of class istreambuf_iterator with a non-null stored pointer, the object effectively attempts to extract and store an object of type E from the associated itput stream. (The extraction may be delayed, however, until the object is actually dereferenced or copied.) If the extraction fails, the object effectively replaces the stored pointer with a null pointer (thus making an end-of-sequence indicator).

istreambuf_iterator::char_type

   typedef E char_type;

The type is a synonym for the template parameter E.

istreambuf_iterator::equal

   bool equal(const istreambuf_iterator& rhs) const;

The member function returns true only if the stored stream buffer pointers for the object and rhs are both null pointers or are both non-null pointers.

istreambuf_iterator::int_type

   typedef typename T::int_type int_type;

The type is a synonym for T::int_type.

istreambuf_iterator::istream_type

   typedef basic_istream<E, T> istream_type;

The type is a synonym for basic_istream<E, T>.

istreambuf_iterator::istreambuf_iterator

   istreambuf_iterator(streambuf_type *sb = 0) throw();
   istreambuf_iterator(istream_type& is) throw();

The first constructor initializes the input stream-buffer pointer with sb. The second constructor initializes the input stream-buffer pointer with is.rdbuf(), then (eventually) attempts to extract and store an object of type E.

istreambuf_iterator::operator*

   const E& operator*() const;

The operator returns the stored object of type E.

istreambuf_iterator::operator++

   istreambuf_iterator& operator++();
   istreambuf_iterator operator++(int);

The first operator (eventually) attempts to extract and store an object of type E from the associated input stream. The second operator makes a copy of the object, increments the object, then returns the copy.

istreambuf_iterator::operator->

   const E *operator->() const;

The operator returns &**this.

istreambuf_iterator::streambuf_type

   typedef basic_streambuf<E, T> streambuf_type;

The type is a synonym for basic_streambuf<E, T>.

istreambuf_iterator::traits_type

   typedef T traits_type;

The type is a synonym for the template parameter T.

iterator

   template<class C, class T, class Dist = ptrdiff_t
       class Pt = T *, class Rt = T&>
       struct iterator {
       typedef C iterator_category;
       typedef T value_type;
       typedef Dist difference_type;
       typedef Pt pointer;
       typedef Rt reference;
       };

The template class serves as a base type for all iterators. It defines the member types iterator_category (a synonym for the template parameter C), value_type (a synonym for the template parameter T), difference_type (a synonym for the template parameter Dist), pointer (a synonym for the template parameter Pt), and reference (a synonym for the template parameter T).

Note that value_type should not be a constant type even if pointer points at an object of const type and reference designates an object of const type.

iterator_traits

   template<class It>
       struct iterator_traits {
       typedef typename It::iterator_category iterator_category;
       typedef typename It::value_type value_type;
       typedef typename It::difference_type difference_type;
       typedef typename It::pointer pointer;
       typedef typename It::reference reference;
       };
   template<class T>
       struct iterator_traits<T *> {
       typedef random_access_iterator_tag iterator_category;
       typedef T value_type;
       typedef ptrdiff_t difference_type;
       typedef T *pointer;
       typedef T& reference;
       };
   template<class T>
       struct iterator_traits<const T *> {
       typedef random_access_iterator_tag iterator_category;
       typedef T value_type;
       typedef ptrdiff_t difference_type;
       typedef const T *pointer;
       typedef const T& reference;
       };

The template class determines several critical types associated with the iterator type It. It defines the member types iterator_category (a synonym for It::iterator_category), value_type (a synonym for It::value_type), difference_type (a synonym for It::difference_type), pointer (a synonym for It::pointer), and reference (a synonym for It::reference).

The partial specializations determine the critical types associated with an object pointer type T *. In this implementation, you can also use several template functions that do not make use of partial specialization:

   template<class C, class T, class Dist>
       C _Iter_cat(const iterator<C, T, Dist>&);
   template<class T>
       random_access_iterator_tag _Iter_cat(const T *);

   template<class C, class T, class Dist>
       T *_Val_type(const iterator<C, T, Dist>&);
   template<class T>
       T *_Val_type(const T *);

   template<class C, class T, class Dist>
       Dist *_Dist_type(const iterator<C, T, Dist>&);
   template<class T>
       ptrdiff_t *_Dist_type(const T *);

which determine several of the same types a bit more indirectly. You use these functions as arguments on a function call. Their sole purpose is to supply a useful template class parameter to the called function.

operator!=

   template<class RanIt>
       bool operator!=(
           const reverse_iterator<RanIt>& lhs,
           const reverse_iterator<RanIt>& rhs);
   template<class U, class E, class T, class Dist>
       bool operator!=(
           const istream_iterator<U, E, T, Dist>& lhs,
           const istream_iterator<U, E, T, Dist>& rhs);
   template<class E, class T>
       bool operator!=(
           const istreambuf_iterator<E, T>& lhs,
           const istreambuf_iterator<E, T>& rhs);

The template operator returns !(lhs == rhs).

operator==

   template<class RanIt>
       bool operator==(
           const reverse_iterator<RanIt>& lhs,
           const reverse_iterator<RanIt>& rhs);
   template<class U, class E, class T, class Dist>
       bool operator==(
           const istream_iterator<U, E, T, Dist>& lhs,
           const istream_iterator<U, E, T, Dist>& rhs);
   template<class E, class T>
       bool operator==(
           const istreambuf_iterator<E, T>& lhs,
           const istreambuf_iterator<E, T>& rhs);

The first template operator returns true only if lhs.current == rhs.current. The second template operator returns true only if both lhs and rhs store the same stream pointer. The third template operator returns lhs.equal(rhs).

operator<

   template<class RanIt>
       bool operator<(
           const reverse_iterator<RanIt>& lhs,
           const reverse_iterator<RanIt>& rhs);

The template operator returns rhs.current < lhs.current [sic].

operator<=

   template<class RanIt>
       bool operator<=(
           const reverse_iterator<RanIt>& lhs,
           const reverse_iterator<RanIt>& rhs);

The template operator returns !(rhs < lhs).

operator>

   template<class RanIt>
       bool operator>(
           const reverse_iterator<RanIt>& lhs,
           const reverse_iterator<RanIt>& rhs);

The template operator returns rhs < lhs.

operator>=

   template<class RanIt>
       bool operator>=(
           const reverse_iterator<RanIt>& lhs,
           const reverse_iterator<RanIt>& rhs);

The template operator returns !(lhs < rhs).

operator+

   template<class RanIt>
       reverse_iterator<RanIt> operator+(Dist n,
           const reverse_iterator<RanIt>& rhs);

The template operator returns rhs + n.

operator-

   template<class RanIt>
       Dist operator-(
           const reverse_iterator<RanIt>& lhs,
           const reverse_iterator<RanIt>& rhs);

The template operator returns rhs.current - lhs.current [sic].

ostream_iterator

char_type , traits_type , ostream_type , ostream_iterator , ostream_iterator , operator= , operator* , operator++ , operator++

   template<class U, class E = char,
       class T = char_traits<E>  >
       class ostream_iterator
           : public iterator<output_iterator_tag,
               void, void, void, void> {
   public:
       typedef E char_type;
       typedef T traits_type;
       typedef basic_ostream<E, T> ostream_type;
       ostream_iterator(ostream_type& os);
       ostream_iterator(ostream_type& os, const E *delim);
       ostream_iterator<U, E, T>& operator=(const U& val);
       ostream_iterator<U, E, T>& operator*();
       ostream_iterator<U, E, T>& operator++();
       ostream_iterator<U, E, T> operator++(int);
       };

The template class describes an output iterator object. It inserts objects of class U into an output stream, which it accesses via an object it stores, of type pointer to basic_ostream<E, T>. It also stores a pointer to a delimiter string, a null-terminated string of elements of type E, which is appended after each insertion. (Note that the string itself is not copied by the constructor.

ostream_iterator::char_type

   typedef E char_type;

The type is a synonym for the template parameter E.

ostream_iterator::operator*

   ostream_iterator<U, E, T>& operator*();

The operator returns *this.

ostream_iterator::operator++

   ostream_iterator<U, E, T>& operator++();
   ostream_iterator<U, E, T> operator++(int);

The operators both return *this.

ostream_iterator::operator=

   ostream_iterator<U, E, T>& operator=(const U& val);

The operator inserts val into the output stream associated with the object, then returns *this.

ostream_iterator::ostream_iterator

   ostream_iterator(ostream_type& os);
   ostream_iterator(ostream_type& os, const E *delim);

The first constructor initializes the output stream pointer with &os. The delimiter string pointer designates an empty string. The second constructor initializes the output stream pointer with &os and the delimiter string pointer with delim.

ostream_iterator::ostream_type

   typedef basic_ostream<E, T> ostream_type;

The type is a synonym for basic_ostream<E, T>.

ostream_iterator::traits_type

   typedef T traits_type;

The type is a synonym for the template parameter T.

ostreambuf_iterator

char_type , traits_type , streambuf_type , ostream_type , ostreambuf_iterator , ostreambuf_iterator , operator= , operator* , operator++ , operator++ , failed

   template<class E, class T = char_traits<E> >
       class ostreambuf_iterator
           : public iterator<output_iterator_tag,
               void, void, void, void> {
   public:
       typedef E char_type;
       typedef T traits_type;
       typedef basic_streambuf<E, T> streambuf_type;
       typedef basic_ostream<E, T> ostream_type;
       ostreambuf_iterator(streambuf_type *sb) throw();
       ostreambuf_iterator(ostream_type& os) throw();
       ostreambuf_iterator& operator=(E x);
       ostreambuf_iterator& operator*();
       ostreambuf_iterator& operator++();
       T1 operator++(int);
       bool failed() const throw();
       };

The template class describes an output iterator object. It inserts elements of class E into an output stream buffer, which it accesses via an object it stores, of type pointer to basic_streambuf<E, T>.

ostreambuf_iterator::char_type

   typedef E char_type;

The type is a synonym for the template parameter E.

ostreambuf_iterator::failed

   bool failed() const throw();

The member function returns true only if no insertion into the output stream buffer has earlier failed.

ostreambuf_iterator::operator*

   ostreambuf_iterator& operator*();

The operator returns *this.

ostreambuf_iterator::operator++

   ostreambuf_iterator& operator++();
   T1 operator++(int);

The first operator returns *this. The second operator returns an object of some type T1 that can be converted to ostreambuf_iterator<E, T>.

ostreambuf_iterator::operator=

   ostreambuf_iterator& operator=(E x);

The operator inserts x into the associated stream buffer, then returns *this.

ostreambuf_iterator::ostream_type

   typedef basic_ostream<E, T> ostream_type;

The type is a synonym for basic_ostream<E, T>.

ostreambuf_iterator::ostreambuf_iterator

   ostreambuf_iterator(streambuf_type *sb) throw();
   ostreambuf_iterator(ostream_type& os) throw();

The first conttructor initializes the output stream-buffer pointer with sb. The second constructor initializes the output stream-buffer pointer with os.rdbuf(). (The stored pointer must not be a null pointer.)

ostreambuf_iterator::streambuf_type

   typedef basic_streambuf<E, T> streambuf_type;

The type is a synonym for basic_streambuf<E, T>.

ostreambuf_iterator::traits_type

   typedef T traits_type;

The type is a synonym for the template parameter T.

output_iterator_tag

   struct output_iterator_tag {
       };

The type is the same as iterator<It>::iterator_category when It describes an object that can serve as a output iterator.

random_access_iterator_tag

   struct random_access_iterator_tag
       : public bidirectional_iterator_tag {
       };

The type is the same as iterator<It>::iterator_category when It describes an object that can serve as a random-access iterator.

reverse_iterator

iterator_type , reverse_iterator , reverse_iterator , reverse_iterator , base , operator* , operator-> , operator++ , operator++ , operator-- , operator-- , operator+= , operator+ , operator-= , operator- , operator[] , containers

   template<class RanIt>
       class reverse_iterator : public iterator<
           typename iterator_traits<RanIt>::iterator_category,
           typename iterator_traits<RanIt>::value_type,
           typename iterator_traits<RanIt>::difference_type,
           typename iterator_traits<RanIt>::pointer,
           typename iterator_traits<RanIt>::reference> {
       typedef typename iterator_traits<RanIt>::difference_type
           Dist;
       typedef typename iterator_traits<RanIt>::pointer
           Ptr;
       typedef typename iterator_traits<RanIt>::reference
           Ref;
   public:
       typedef RanIt iterator_type;
       reverse_iterator();
       explicit reverse_iterator(RanIt x);
       template<class U>
           reverse_iterator(const reverse_iterator<U>& x);
       RanIt base() const;
       Ref operator*() const;
       Ptr operator->() const;
       reverse_iterator& operator++();
       reverse_iterator operator++(int);
       reverse_iterator& operator--();
       reverse_iterator operator--();
       reverse_iterator& operator+=(Dist n);
       reverse_iterator operator+(Dist n) const;
       reverse_iterator& operator-=(Dist n);
       reverse_iterator operator-(Dist n) const;
       Ref operator[](Dist n) const;
   protected:
       RanIt current;
       };

The template class describes an object that behaves like a random-access iterator, only in reverse. It stores a random-access iterator of type RanIt in the protected object current. Incrementing the object x of type reverse_iterator decrements x.current, and decrementing x increments x.current. Moreover, the expression *x evaluates to *(current - 1), of type Ref. Typically, Ref is type T&.

Thus, you can use an object of class reverse_iterator to access in reverse order a sequence that is traversed in order by a random-access iterator.

Several STL containers specialize reverse_iterator for RanIt a bidirectional iterator. In these cases, you must not call any of the member functions operator+=, operator+, operator-=, operator-, or operator[].

reverse_iterator::base

   RanIt base() const;

The member function returns current.

`reverse_iterator::iterator_type`

   typedef RanIt iterator_type;

The type is a synonym for the template parameter RanIt.

reverse_iterator::operator*

   Ref operator*() const;

The operator returns *(current - 1).

reverse_iterator::operator+

   reverse_iterator operator+(Dist n) const;

The operator returns reverse_iterator(*this) += n.

reverse_iterator::operator++

   reverse_iterator& operator++();
   reverse_iterator operator++(int);

The first (preincrement) operator evaluates --current. then returns *this.

The second (postincrement) operator makes a copy of *this, evaluates --current, then returns the copy.

reverse_iterator::operator+=

   reverse_iterator& operator+=(Dist n);

The operator evaluates current - n. then returns *this.

reverse_iterator::operator-

   reverse_iterator operator-(Dist n) const;

The operator returns reverse_iterator(*this) -= n.

reverse_iterator::operator--

   reverse_iterator& operator--();
   reverse_iterator operator--();

The first (predecrement) operator evaluates ++current. then returns *this.

The second (postdecrement) operator makes a copy of *this, evaluates ++current, then returns the copy.

reverse_iterator::operator-=

   reverse_iterator& operator-=(Dist n);

The operator evaluates current + n. then returns *this.

reverse_iterator::operator->

   Ptr operator->() const;

The operator returns &**this.

reverse_iterator::operator[]

   Ref operator[](Dist n) const;

The operator returns *(*this + n).

`reverse_iterator::pointer`

   typedef Ptr pointer;

The type is a synonym for the template parameter Ref.

`reverse_iterator::reference`

   typedef Ref reference;

The type is a synonym for the template parameter Ref.

`reverse_iterator::reverse_iterator`

   reverse_iterator();
   explicit reverse_iterator(RanIt x);
   template<class U>
       reverse_iterator(const reverse_iterator<U>& x);

The first constructor initializes current with its default constructor. The second constructor initializes current with x.current.

The template constructor initializes current with x.base().

iterator(3C++std)

Synopsis

Description

References