Standard C++ Library Class Reference

Description

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.