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| Category: iterators | Component type: type |
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.
| Parameter | Description | Default |
|---|---|---|
| T | The iterator's value type | |
| Distance | The iterator's distance type | ptrdiff_t |
[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.
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