Iterator Concepts

From Cppreference

[edit] Notation

In the following, as in the standard, the following notation is used:

• X is the iterator type being discussed
• a and b are instances of the iterator, with type X
• reference refers to iterator_traits<X>::reference
• difference_type refers to iterator_traits<X>::difference_type

[edit] Iterator Requirements

Iterator is a general concept that does not guarantee much beyond the ability to advance and dereference elements. Formally, an iterator has the following requirements:

• CopyConstructable
• CopyAssignable
• Destructible
• Swappable

In addition, the following expressions are valid:

• *a returns type reference as long as the itearator is dereferencable,
• ++a returns X&.

Examples:

• All iterators in the standard library model the Iterator concept.

[edit] InputIterator Requirements

A class X satisfies the requirements of an InputIterator for the value type T if X satisfies the Iterator and EqualityComparable requirements and the following expressions are valid:

• a!=b is convertible to bool as long as (a,b) is in the domain of == operator,
• *a returns type reference as long as the itearator is dereferencable,
• a->m() is equivalent to (*a).m(),
• ++a returns X&,
• a++ is equivalent to ++a,
• *(a++) is equivalent to

{
  T tmp = *a;
  ++a;
  return a;
}

[edit] OutputIterator Requirements

A class X satisfies the requirements of an OutputIterator if X satisfies the Iterator requirements.

[edit] ForwardIterator Requirements

[edit] BidirectionalIterator Requirements

[edit] RandomAccessIterator Requirements