forward_iterator<T, Distance>


Category: iterators	Component type: type

Description

Forward_iterator is an iterator base class: it is intended that an iterator that is a model of Forward Iterator, and whose value type and distance type are T and Distance, may be defined by inheriting from forward_iterator<T, Distance> [1]. Forward_iterator is entirely empty: it has no member functions, member variables, or nested types. It exists solely to simplify the definition of the functions iterator_category, distance_type, and value_type.

Example

class my_forward_iterator : public forward_iterator<double> 
{
  ...
};

This declares my_forward_iterator to be a Forward Iterator whose value type is double and whose distance type is ptrdiff_t. If Iter is an object of class my_forward_iterator, then iterator_category(Iter) will return forward_iterator_tag(), value_type(Iter) will return (double*) 0, and distance_type(Iter) will return (ptrdiff_t*) 0.

Definition

Defined in the standard header iterator, and in the nonstandard backward-compatibility header iterator.h. This class is no longer part of the C++ standard, although it was present in early drafts of the standard. It is retained in this implementation for backward compatibility.

Template parameters

Parameter	Description	Default
`T`	The iterator's value type
`Distance`	The iterator's distance type	`ptrdiff_t`

Model of

Assignable

Public base classes

None

Type requirements

The distance type must be a signed integral type.

Public base classes

None.

Members

None.

New Members

None.

Notes

[1] It is not required that a Forward Iterator inherit from the base forward_iterator. It is, however, required that the functions iterator_category, distance_type, and value_type be defined for every Forward Iterator. (Or, if you are using the iterator_traits mechanism, that iterator_traits is properly specialized for every Forward Iterator.) Since those functions are defined for the base forward_iterator, the easiest way to ensure that are defined for a new type is to derive that class from forward_iterator and rely on the derived-to-base standard conversion of function arguments.

forward_iterator<T, Distance>

Description

Example

Definition

Template parameters

Model of

Public base classes

Type requirements

Public base classes

Members

New Members

Notes

See also