libs/type_traits/examples/iter_swap_example.cpp
/*
*
* (C) Copyright John Maddock 1999-2005.
* Use, modification and distribution are subject to the
* Boost Software License, Version 1.0. (See accompanying file
* LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
*
* This file provides some example of type_traits usage -
* by "optimising" various algorithms:
*
* opt::iter_swap - uses type_traits to determine whether the iterator is a proxy
* in which case it uses a "safe" approach, otherwise calls swap
* on the assumption that swap may be specialised for the pointed-to type.
*
*/
#include <iostream>
#include <typeinfo>
#include <algorithm>
#include <iterator>
#include <vector>
#include <memory>
#include <boost/test/included/prg_exec_monitor.hpp>
#include <boost/type_traits.hpp>
using std::cout;
using std::endl;
using std::cin;
namespace opt{
//
// iter_swap:
// tests whether iterator is a proxy iterator or not, and
// uses optimal form accordingly:
//
namespace detail{
template <typename I>
static void do_swap(I one, I two, const boost::false_type&)
{
typedef typename std::iterator_traits<I>::value_type v_t;
v_t v = *one;
*one = *two;
*two = v;
}
template <typename I>
static void do_swap(I one, I two, const boost::true_type&)
{
using std::swap;
swap(*one, *two);
}
}
template <typename I1, typename I2>
inline void iter_swap(I1 one, I2 two)
{
//
// See is both arguments are non-proxying iterators,
// and if both iterator the same type:
//
typedef typename std::iterator_traits<I1>::reference r1_t;
typedef typename std::iterator_traits<I2>::reference r2_t;
typedef boost::integral_constant<bool,
::boost::is_reference<r1_t>::value
&& ::boost::is_reference<r2_t>::value
&& ::boost::is_same<r1_t, r2_t>::value> truth_type;
detail::do_swap(one, two, truth_type());
}
}; // namespace opt
int cpp_main(int argc, char* argv[])
{
//
// testing iter_swap
// really just a check that it does in fact compile...
std::vector<int> v1;
v1.push_back(0);
v1.push_back(1);
std::vector<bool> v2;
v2.push_back(0);
v2.push_back(1);
opt::iter_swap(v1.begin(), v1.begin()+1);
opt::iter_swap(v2.begin(), v2.begin()+1);
return 0;
}