On 12/06/07 16:07, Andreas Harnack wrote: [snip]
Jens Seidel schrieb: [snip]
Nearly always the dimensions are variables, there are only a few rare cases where you know these before. So how about making N and M variables and providing one or two good memory allocators?
T* data() { return &**m; }
Why not &m[0][0]?
Just a matter of taste, I guess. Actually I'm not even sure yet that it's wise to use a two dimensional array at all. T m[M*N] would work equally well and since there's no interface yet that relies on that structure, the latter might even be the simpler approach. The two-dimensional array just felt to be more 'natural' for a matrix. (whatever that means :-) ) I think n-dimension would be pretty easy. Instead of:
template<typename T, unsigned int M, unsigned int N> class matrix { ... }; you could provide: template<typename Value, typename Shape> class array_fix_shape { ... }; where, using concepts maybe, you could constrain Shape to be some instance of mpl::vector_c<unsigned,S0,S1,...,Sn>. Then, the rank of array_fix_size would be Shape::size. You could calculate of strides using some mpl metafunction on Shape: typedef some-mpl-function < Shape >::type strides ; and then allocate storage as: Value values [ mpl::at_c<strides,Strides::size>::value ] ; Then operator[] could be defined as: Value& operator[](boost::array<unsigned,Shape::size>const& indices) { return values[some_offset_function_<strides>(indices)]; } where some_offset_function simply performs a dot product of the compile time vector, strides, with the runtime vector, indices.