c++ - Template class constructor not working -

from other question here copying std container frm arbitrary source object managed template working under msvc. unfortunately compiler crashes newest addtion of adding constructor accept kind of std containers, , real project in gcc anyway. when use template in gcc, several errors don't know how resolve.

template <class t> class readonlyiterator { public:     template <typename v, typename u>     struct is_same     {         enum { value = 0 };     };      template <typename v>     struct is_same<v, v>     {         enum { value = 1 };     };      template <bool, typename>     struct enable_if     {};      template <typename v>     struct enable_if<true, v>     {         typedef v type;     };  template <typename container>     typename enable_if<     is_same<t, typename container::value_type>::value, readonlyiterator<t>&>::type operator= (const container &v)     {         return *this;     }      template <typename container>     readonlyiterator(const container &v, typename enable_if<is_same<t, typename container::value_type>::value, void>::type * = 0)     {         mvector = v;         mbegin = mvector.begin();     } }; 

my goal allow assignments this:

std::vector<simpleclass *>v; std::list<simpleclass *>l; readonlyiterator<simpleclass *> t0 = v; readonlyiterator<simpleclass *> &t1 = v; readonlyiterator<simpleclass *> t2 = readonlyiterator<simpleclass *>(v); readonlyiterator<simpleclass *> t3 = l;  t0 = v; t0 = l; 

i updated code above , reverted wrong changes applied. original problem tried fix:

readonlyiterator<simpleclass *> &t1 = v; 

leads to:

invalid initialization of reference of type 'readonlyiterator<simpleclass*>&' expression of type 'std::vector<simpleclass*, std::allocator<simpleclass*> >' 

as found out, if write template class within template class, have give template parameters different names:

template <typename u, typename v> struct is_same<u, v> {     enum { value = 0 }; }; 

in specialization of is_same, have use same types when specifying specialized class name (you can name u, use same name on 3 places: in template parameter list in specialized class name):

template <typename v> struct is_same<v, v> {     enum { value = 1 }; }; 

also, mentioned in comments, should make these helper-classes struct instead of class; don't have write public:.