calling stationary member duty c++ stl container's value

i'm perplexing conduct around since following doesn't work. i have std::vector i wish stationary member duty it's contained value_type so:

std::vector<vector> v;
unsigned u = v.value_type::dim();

where settlement fact typedef templated type:

template <typename t, unsigned u> category svector; 
typedef svector<double, 2> vector; //two-dimensional svector containing doubles

and stationary member duty dim() indeed inlines dimensionality u vector.

now compiler advantage an blunder summary saying:

 error: svector<double, 2u> bottom 
 std::vector<svector<double, 2u>, std::allocator<svector<double, 2u> > >

which puzzles me. i reinstate apparently offending line by

unsigned u = vector::dim();

and works, nonetheless apparently dizzy hardcodes assumptions value_type v...
thanks!

code1