class my_input_iterator : public input_iterator<double> {
…
};
This declares my_input_iterator to be an Input Iterator whose value type is double and whose distance type is ptrdiff_t. If Iter is an object of class my_input_iterator, then iterator_category(Iter) will return input_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 an Input Iterator inherit from the base input_iterator. It is, however, required that the functions iterator_category, distance_type, and value_type be defined for every Input Iterator. (Or, if you are using the iterator_traits mechanism, that iterator_traits is properly specialized for every Input Iterator.) Since those functions are defined for the base input_iterator, the easiest way to ensure that are defined for a new iterator class is to derive that class from input_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, output_iterator, forward_iterator, bidirectional_iterator, random_access_iterator
Category: iterators
Component type: type
Description Output_iterator is an iterator base class: it is intended that an iterator that is a model of Output Iterator may be defined by inheriting from output_iterator [1]. Output_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_output_iterator : public output_iterator {
…
};
This declares my_output_iterator to be an Output Iterator. If Iter is an object of class my_output_iterator, then iterator_category(Iter) will return output_iterator_tag(), and distance_type and value_type will be undefined for objects of class my_output_iterator.
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 None. (Note that Output Iterators need have neither distance types nor value types.)
Model of Assignable
Public base classes None
Type requirements None.
Public base classes None.
Members None.
New Members None.
Notes 
