Question

I require a linear vector container to behave like a multi-dimensional vector container. That is, a vector such as std::vector< std::vector< std::vector<int> > > be declared as std::vector<int> but behave as if it is multi-dimensional. This requires that I have set and get functions that allow accessing by multiple indices, rather than just one (that is, x, y, z and not just i).

The conversion is not the problem (that is, converting a 3D or 2D index to 1D), I am already doing that. However, I am starting to require the same conversion for several arrays. To make matters more complicated, I require a linear array to behave as if it is 2D, 3D and 4D. Now I want to make a container that will take care of the conversion internally. For all intents and purposes, the container will look like it is multi-dimensional, but it is in fact a linear array underneath.

So, first of, I am not sure whether libraries like boost have already something similar implemented. If so, please point me in the right direction. If not, then I would like to create one for my use but have a few questions.

My current approach is to make a class that has a vector container. There is a GetVec() function that will return the address of the std::vector so that I don’t have to write all the functions that std::vector already has (getting the iterators, size etc.).

I want the user to be able to use the container from 1-D to N-D. When accessing, the user should be allowed to pass indexes that can represent a 1-D array or an N-D array. How do I ensure that the user is passing the correct number of indexes (in the function parameters)? Also, when initializing, the user should be able to specify the dimensions (variable parameter list?).

If this is a bad idea in general, please let me know but with good reasons. If not, any pointers on how to go about implementing this class would be much appreciated.

Answer 1

You have two choices: std::valarray (and its splice adapters), or boost::multi_array.

The first one lacks many things, and is not often used (it should deserve more love though). The second one is heavy but quite clean to use.

Also, you can have a look at Eigen if you intend to do linear algebra on those beasts.

I can also mention Intel Array Building Blocks which is simply awesome, and could be what you want in fine. It depends on what you do with those containers.