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                       Standard C++ Library
             Copyright 1998, Rogue Wave Software, Inc.


NAME
     __distance_type

      - Determines the type of distance used by an iterator. This
     function is now obsolete. It is retained in order to include
     backward compatibility and support  compilers  that  do  not
     include partial specialization.



SYNOPSIS
     #include <iterator>
     template <class Category, class T, class Distance,
              class Pointer, class Reference>
     inline Distance* __distance_type(const iterator<Category, T,
                     Distance, Pointer, Reference>&);
     template <class T>
     inline ptrdiff_t* __distance_type (const T*);



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  of
     these  take  an  iterator  of a particular type and return a
     pointer to a default value of the difference_type  for  that
     iterator. The T* form of the function returns ptrdiff_t*.

     Generic algorithms use this function to create  local  vari-
     ables 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.



SEE ALSO
     Other       iterator        primitives:        __value_type,
     __iterator_category, distance, advance

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