Iterators

Iterators are modeled after standard C pointers.

Typical pointer usage:

  char buf[20];
  ... //assign some value
  for (char* i = buf;
       *i != '\0';
       i++)
			*i = toupper(*i);

Typical iterator usage:

  vector < char > buf;
  ... //assign some value
  for (vector < char >::iterator i=buf.begin();
       i!=buf.end();
       i++)
			*i = toupper(*i);

Standard C pointers work on STL vector<>s too!
Iterators are the interface that the STL generic algorithms use to work with any container!

Random Access Iterators

Most closely resembles the standard C pointer.

Bidirectional Iterators

Use to traverse containers in either direction.

Forward Iterators

Use to traverse containers in one direction only.

Input Iterators

Can only read elements, and in the forward direction only.

Output Iterators

Can only write elements.

Operators supported by the iterator types

operator	input	output	forword	bidirect	random
_ == _	x		x	x	x
_ != _	x		x	x	x
* _	x		x	x	x
++ _	x	x	x	x	x
_ ++	x	x	x	x	x
_ = _		x	x	x	x
-- _				x	x
_ --				x	x
_ +=(int)					x
(int)+ _					x
_ +(int)					x
_ -=					x
_ - (int)					x
int:_ - _					x
_ [ _ ]					x
_ < _					x
_ > _					x
_ >= _					x
_ <= _					x

Stream Iterators

istream_iterator

  ...
  istream_iterator < string, ptrdiff_t > in(cin);
  istream_iterator < string, ptrdiff_t > end;
  while (in != end) cout << *in++;
  ...

ostream_iterator

  ...
  ostream_iterator < string, ptrdiff_t > out(cout);
  copy(in, end, out);
  ...

Iterator Adaptors

reverse_iterator
- merely adapts the ++/-- operators (and related ones) to --/++
back_insert_iterator
- use with vector, deque, or list
- back_inserter(Container&) builds one
front_insert_iterator (deque, list)
- use with deque, or list
- front_inserter(Container&) builds one
insert_iterator
- use with list
- inserter(Container&, Iterator) builds one
raw_storage_iterator
- use internally by STL in some generic algorithms

Iterators

Random Access Iterators

Bidirectional Iterators

Forward Iterators

Input Iterators

Output Iterators

Operators supported by the iterator types

operator

input

output

forword

bidirect

random

Stream Iterators

Iterator Adaptors