distance.cpp

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#include <cassert>
#include <iterator>
#include <iostream>
#include <vector>
 
#include <examples.h>
 
 
int main ()
{
    // Typedefs for convenience.
    typedef std::vector<int, std::allocator<int> > Vector;
 
    typedef std::ostream_iterator<Vector::value_type,
                                  char,
                                  std::char_traits<char> > os_iter;
 
    // Initialize a vector using an array.
    const Vector::value_type arr [] = { 3, 4, 5, 6, 7, 8 };
    const Vector v (arr + 0, arr + sizeof arr/ sizeof *arr);
 
    // Declare a vector iterator, s.b. a ForwardIterator.
    Vector::const_iterator it = v.begin () + 3;
 
    // Output the original vector.
    std::cout << "For the vector: ";
    std::copy (v.begin (), v.end (), os_iter (std::cout, " "));
    std::cout << '\n';
 
    std::cout << "\nWhen the iterator is initialized to point to "
              << *it << '\n';
 
    // Compute the distance of it from the first element.
    Vector::difference_type dist = 0;
 
#ifndef _RWSTD_NO_EXT_VOID_DISTANCE
 
    // using the extended overload of function template distance()
    // provided by this implmentation, compute the distance between
    // the two iterators
    std::distance (v.begin (), it, dist);
 
    assert (3 == dist);
 
#endif   // _RWSTD_NO_EXT_VOID_DISTANCE
 
    // do the same using the standard function template distance()
    dist = std::distance (v.begin (), it);
 
    std::cout << "The distance between the beginning and "
              << *it << " is " << dist << '\n';
 
    return 0;
}