distance_type

Iterator primitive

• Summary
• Data Type and Member Function Indexes
• Synopsis
• Description
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Determine the type of distance used by an iterator. This function is now obsolete. It is retained in order to provide backward compatibility and support compilers that do not provide partial specialization.

None

#include <iterator>

template <class T, class Distance> 
inline Distance* distance_type (const input_iterator<T,
      Distance>&)

template <class T, class Distance> 
inline Distance* distance_type (const forward_iterator<T,
      Distance>&)

template <class T, class Distance> 
inline Distance* 
distance_type (const bidirectional_iterator<T, Distance>&)

template <class T, class Distance>
inline Distance* 
distance_type (const random_access_iterator<T, Distance>&)

template <class T>
inline ptrdiff_t* distance_type (const T*)

The distance_type family of function templates return a pointer to a value that is of the same type as that used to represent a distance between two iterators. The first four of these take an iterator of a particular type and return a pointer to a default value of the distance_type for that iterator. The T* form of the function returns ptrdiff_t*.

Generic algorithms use this function to create local variables of the correct type. The distance_type functions are typically used like this:

template <class Iterator>
void foo(Iterator first, Iterator last)
{
  __foo(begin,end,distance_type(first));
}

template <class Iterator, class Distance>
void __foo(Iterator first, Iterator last, Distance*>
{
  Distance d = Distance();
  distance(first,last,d);
  _
}

The auxiliary function template allows the algorithm to extract a distance type from the first iterator and then use that type to perform some useful work.

Other iterator primitives: value_type, iterator_category, distance, advance

©Copyright 1996, Rogue Wave Software, Inc.