value_type (3C++std) - Tru64 UNIX
Standard C++ LibraryCopyright 1996, Rogue Wave Software, Inc. NAME
value_type - Determine the type of value an iterator points to. This
function is now obsolete. It is retained in order to provide backward
compatibility and support compilers that do not provide partial
specialization.
SYNOPSIS
#include <iterator>
template <class T, class Distance>
inline T* value_type (const input_iterator<T, Distance>&)
template <class T, class Distance>
inline T* value_type (const forward_iterator<T, Distance>&)
template <class T, class Distance>
inline T* value_type (const bidirectional_iterator<T, Distance>&)
template <class T, class Distance>
inline T* value_type (const random_access_iterator<T, Distance>&)
template <class T>
inline T* value_type (const T*)
DESCRIPTION
The value_type function template returns a pointer to a default value of
the type pointed to by an iterator. Five overloaded versions of this
function template handle the four basic iterator types and simple arrays.
Each of the first four take an iterator of a specific type, and return the
value used to instantiate the iterator. The fifth version takes and
returns a T* in order to handle the case when an iterator is a simple
pointer.
This family of function templates can be used to extract a value type from
an iterator and subsequently use that type to create a local variable.
Typically the value_type functions are used like this:
template <class Iterator>
void foo(Iterator first, Iterator last)
{
__foo(begin,end,value_type(first));
}
template <class Iterator, class T>
void __foo(Iterator first, Iterator last, T*>
{
T temp = *first;
_
}
The auxiliary function __foo extracts a usable value type from the iterator
and then puts the type to work.
SEE ALSO
Other iterator primitives: distance_type, iterator_category, distance,
advance
STANDARDS CONFORMANCE
ANSI X3J16/ISO WG21 Joint C++ Committee
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