开始学习模板元编程了
#include <iostream> #include <string> #include <vector> #include <list> #include "boost/assign/list_of.hpp" #include "boost/type_traits/is_const.hpp" #include "boost/type_traits/is_reference.hpp" #include "boost/type_traits/is_same.hpp" #include "boost/shared_ptr.hpp" namespace swap_test { template<bool use_swap> struct use_swap_impl; template<typename ForwardIterator1, typename ForwardIterator2> static void swap_iter(ForwardIterator1& i1, ForwardIterator2& i2) { typedef std::iterator_traits<ForwardIterator1> trait1; typedef typename trait1::value_type v1; typedef typename trait1::reference r1; typedef std::iterator_traits<ForwardIterator2> trait2; typedef typename trait2::value_type v2; typedef typename trait2::reference r2; bool const use_swap = boost::is_same<v1, v2>::value && boost::is_reference<r1>::value && boost::is_reference<r2>::value;//防止代理引用vector<bool>的迭代器,见mpl page30. use_swap_impl<use_swap>::to_do_swap(i1, i2); } template<>//两种类型是一样的, struct use_swap_impl<true> { template<typename ForwardIterator1, typename ForwardIterator2> static void to_do_swap(ForwardIterator1& i1, ForwardIterator2& i2) { std::swap(*i1, *i2); } }; template<> struct use_swap_impl<false> { template<typename ForwardIterator1, typename ForwardIterator2> static void to_do_swap(ForwardIterator1& i1, ForwardIterator2& i2) { typename std::iterator_traits<ForwardIterator1>::value_type tmp = *i1; *i1 = *i2; *i2 = tmp; } }; void fun() { std::list<std::string> list = boost::assign::list_of("123")("456"); std::vector<std::string> vec = boost::assign::list_of("789")("013"); swap_iter(list.begin(), vec.begin()); std::cout << *(list.begin()) << " " << *(vec.begin()) << std::endl; boost::shared_ptr<int> t1(new int(18)); boost::shared_ptr<float> t2(new float(20.0f)); int *tt1 = t1.get(); float *tt2 = t2.get(); swap_tier(tt1, tt2); std::cout << *t1 << " " << *t2 << std::endl; } }
meta program (1) swap_iter
时间: 2024-10-13 21:54:20