count.cpp

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#include <algorithm>    // for count, count_if
#include <cassert>      // for assert
#include <functional>   // bind2nd, less
#include <iostream>     // for cout
#include <iterator>     // for ostream_iterator
#include <vector>       // for vector
 
#include <examples.h>
 
 
// streams out a vector
template <class T>
std::ostream&
operator<< (std::ostream &out,
            const std::vector<T, std::allocator<T> > &vec)
{
    typedef std::ostream_iterator<T, char, std::char_traits<char> > Iter;
 
    out << "{ ";
 
    std::copy (vec.begin (), vec.end (), Iter (out, " "));
 
    out << "}";
 
    return out;
}
 
 
int main ()
{
    // Typedef for convenience.
    typedef std::vector<short, std::allocator<short> > Vector;
 
    const Vector::value_type a [] = { 1, 2, 3, 4, 5, 5, 7, 8, 9, 10 };
 
    // construct a vector from the array
    const Vector vec (a + 0, a + 10);
 
    Vector::size_type n_fives = 0;
    Vector::size_type n_sixes = 0;
    Vector::size_type n_lt_8  = 0;
 
#ifndef _RWSTD_NO_EXT_VOID_COUNT
 
    // using the extended overloads of function template count()
    // and count_if() provided by this implmentation, count the
    // number of fives, sixes, and values less than 8 in the
    // sequence
 
    std::count (vec.begin (), vec.end (), 5, n_fives);
    std::count (vec.begin (), vec.end (), 6, n_sixes);
 
    std::count_if (vec.begin (), vec.end (),
                   std::bind2nd (std::less<Vector::value_type>(), 8),
                   n_lt_8);
 
    assert (2 == n_fives);
    assert (0 == n_sixes);
    assert (7 == n_lt_8);
 
#endif   // _RWSTD_NO_EXT_VOID_COUNT
 
    // do the same using the standard function templates count()
    // and count_if()
 
    n_fives = std::count (vec.begin (), vec.end (), 5);
    n_sixes = std::count (vec.begin (), vec.end (), 6);
    n_lt_8  = std::count_if (vec.begin (), vec.end (),
                             std::bind2nd (std::less<Vector::value_type>(), 8));
 
    std::cout << "sequence: " << vec;
    std::cout << "\nnumber of fives: " << n_fives
              << "\nnumber of sixes: " << n_sixes
              << "\nnumber of values less than 8: " << n_lt_8 << '\n';
 
    return 0;
}