基於範圍的STL容器

Question

我使用沉重的BOOST_FOREACH來迭代容器，並且由於我最近搬到了C++ 0x，我以爲我可以用基於範圍的for構造替代BOOST_FOREACH。下面的代碼

#include<vector> 
#include<boost/shared_ptr.hpp> 
#include<boost/range.hpp> 
using std::vector; using boost::shared_ptr; 
class Node; 
int main(void){ 
    vector<shared_ptr<Node>> nodes; 
    for(const shared_ptr<Node>& n: nodes); 
} 

一塊不gcc 4.6編譯，從而導致

error: call of overloaded 'end(std::vector<boost::shared_ptr<Node> >&)' is ambiguous 
note: candidates are: 
/usr/include/c++/4.6/bits/range_access.h:78:5: note: decltype (__cont->end()) std::end(const _Container&) [with _Container = std::vector<boost::shared_ptr<Node> >, decltype (__cont->end()) = __gnu_cxx::__normal_iterator<const boost::shared_ptr<Node>*, std::vector<boost::shared_ptr<Node> > >] 
/usr/include/c++/4.6/bits/range_access.h:68:5: note: decltype (__cont->end()) std::end(_Container&) [with _Container = std::vector<boost::shared_ptr<Node> >, decltype (__cont->end()) = __gnu_cxx::__normal_iterator<boost::shared_ptr<Node>*, std::vector<boost::shared_ptr<Node> > >] 
/usr/include/boost/range/end.hpp:103:47: note: typename boost::range_iterator<const T>::type boost::end(const T&) [with T = std::vector<boost::shared_ptr<Node> >, typename boost::range_iterator<const T>::type = __gnu_cxx::__normal_iterator<const boost::shared_ptr<Node>*, std::vector<boost::shared_ptr<Node> > >] 
/usr/include/boost/range/end.hpp:92:41: note: typename boost::range_iterator<C>::type boost::end(T&) [with T = std::vector<boost::shared_ptr<Node> >, typename boost::range_iterator<C>::type = __gnu_cxx::__normal_iterator<boost::shared_ptr<Node>*, std::vector<boost::shared_ptr<Node> > >] 

是否有辦法避免這種含糊不清，或者是基於範圍在這種情況下根本無法使用？

Answer 1

棘手。您正在撥入std::end和boost::end，因爲std::vector<boost::shared_ptr>的關聯名稱空間都是std和boost。兩者都是匹配的模板。

但是，非模板end()將是更好的匹配。所以，只要提供你自己的：

inline std::vector<boost::shared_ptr<Node> >::iterator 
    end(std::vector<boost::shared_ptr<Node> > vsn&) 
{ 
    return std::end(vsn); 
}