c++ - How to induce some template classes being united by one template? -

i have template classes. united 1 namespace, , depends on each other's template parameter.

that point using #define t instead of template, , use in classes, client classes may want create such pairs different t, why want use templates.

but if create 2 separated classes own separated templates, have chance client make mistake , put different values there. so, avoid it, if possible, make set t once pair of such classes , use both classes it's value.

i create (just imagine):

template<int t> namespace sample {     struct     {         char _data[t];     }      struct b     {         void get(a& a)         {             memcpy(b, a._data, t);         }         char b[t];     } } 

so, there separated classes, if 1 has parameter t = 50, other have work same parameter. best solution - template namespace, c++ has no template namespaces.

is possible make somehow? maybe need pattern?

i don't want add like:

char x1[t1 - t2 + 1]; char x2[t2 - t1 + 1]; 

inside class b, error if t1 != t2 @ compilation, find simple , beauty solution task, believe have exist :-)

use nested classes. replace namespace struct.

template<int t> struct sample {     struct {         char _data[t];     };      struct b{         // ...     };      // can have static methods operate on types     // same template instance without specifying type     static void foo(b& b) {         a{0};         b.get(a);     } };  int main() {     sample<2>::a a{0};     sample<2>::b b;     b.get(a); } 

perhaps remove constructor of sample no 1 tries instantiate it.