c++ - How to define the constructor of an inner template class of another template class? -

i have inner template class of template class:

// hpp file template< class t1 > class c1 {    // ... public:    // ...    c1();    template< class t2 > c2    {       // ...       c2();    }; }; 

when declare inner class constructor errors:

//cpp file template<> c1< mytype >::c1() {    // ... }  template<> template< class t2 > c1< mytype >::c2::c2() // error: invalid use of template-name ‘class c1<mytype>::c2’ without argument list     {    // ... } 

i have tried :

template<> template< class t2 > c1< mytype >::c2<t2>::c2() // error: invalid use of incomplete type ‘class c1<mytype>::c2<t2>’ {    // ... } 

incomplete type, constructor has no type...

i little stuck here. how declare it?

perform following:

template<typename t1> template<typename t2> c1<t1>::c2<t2>::c2() { }