||Component type: type
Input_iterator is an iterator base class: it is intended that an
iterator that is a model of Input Iterator, and whose value type
and distance type are T and Distance, may be defined by inheriting from
input_iterator<T, Distance> . Input_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.
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.
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.
The iterator's value type
The iterator's distance type
Public base classes
The distance type must be a signed integral type.
Public base classes
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.
The Iterator Tags overview, iterator_traits,
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