forward_iterator<T, Distance>
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| 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
AssignablePublic base classes
NoneType 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.
See also
The Iterator Tags overview, iterator_traits, iterator_category, value_type, distance_type, input_iterator, output_iterator, bidirectional_iterator, random_access_iterator![[Silicon Surf]](surf.gif)
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