Thanks for your reply. I've studied things in more detail and I feel a lot better about things now. I think I was just frustrated with the difficulty understanding the documentation. So I'll just make couple of observations. a) Basically I think this package is ideal for the problem that I am attempting apply it to. This made it worthwhile to spend a larger time than I might have otherwise to figure out how it works. User Documentation and Tutorial Short Example - basically OK execept that the typedefs add an extra layer of conceptual redirection which makes less obvious than it should be. MultiArray Components OK - but just mentions views without pointing to any explaination of them. Array View and Subarray Type Generators - Reading through the tutorial and coming upon this is totally mystifying. Creating Views Describes how they are created with out explaining that they are. I looked in vain for a class description of views - either formal or informal. The rest of tutorial is OK Reference Documentation Library Synopsis mentions boost/multi_array.hpp - it would have been nice if there had been a link to the source code header. Now I see this: namespace boost { namespace multi_array_types { typedef *implementation-defined* index; An I have no idea what *implementation-defined* is. I could be defined by the compiler, standard libary implementation or it could be set by my own array instantiation. (This might be be related to a warning I get regarding unsigned int vs size_t when I use the library) Anyway its not at all clear to me. MultiArray Concept - OK this is pretty clear BUT - its not clear what the concept is to be used for. There aren't any other templates which this concept is used to describe a template parameter. On seeing this, along with what I expect views to be, I expected to see something like A(T & t) in "valid expressions" where T is a type modeling MultArray concept. Instead each class modeling this concept has its own list of constructors. So the whole idea of defining a concept seemed sort of like a detour. I suppose this is really a question about the library itself. The library seems to be built on recurrsive ideas - arrays of arrays of higher order, MultiArray classes constructed from other onese, etc. But this doesn't seem to be reflected in the library or the documentation. Models Views are mentioned - but its not initially clear what the relationship is between views, sub arrays and mult_array I tracked down the concept checking classes. They are not mentioned in the documentation - which I could be OK since its not clear how a user would find these useful. Its not obvious that a user would want to make his own model of a MultiArray so it might not seem necessary - more on that below. After struggling through this, the code, and a number of small compilation experiments, I concluded that the library does seem to implement what I originally thought it should implement - and it seems a nice job and complete. So I'm pleased with that I've found - I just don't think it should be so hard. So that's my observations on the multi_array documentation and a little bit on the design. I feel better now. Now there are two things I would like to do with this library. My perusal of the documentation was motivated by the desire to implement them. a) I really need a "join" operator which looks like: template<unsigned int I, class M, class N> array_view<??> join<I>(M & m, N &n); where M and N are classes modeling the MultiArray concept. This function would do the following: i) verify the that the projections of m and n along dimension I have the same shape and fail if they do not. ii) return a view which is the "sticking together" along dimension I of m and n. This is the inverse process of slicing. Should this not exist at this time, I well attempt to implement it. b) I can live without the following - but it would be very cool from my application. The ability to define different extents for subarrays with different indices. Array a1[2]; Array a2[4]; Array a3[2] = {a1, a2}; I suspect that such a think is beyond what the library can be made to do - and its not even clear that it make sense - but its not a big issue for me. Robert Ramey Ronald Garcia wrote:
Hi Robert,
You should be able to create a new instance of a multi_array from a subarray or view reference. Could you show me some specific code that you're having trouble with?
Cheers, ron
On Mar 24, 2006, at 5:18 PM, Robert Ramey wrote:
The multi_array library seems to a good fit for a situation which I'm currently dealing with.
I'm having a lot of problems understanding how to use it though.
I can't really understand the distinction between the differing types of views, subviews etc.
I would sort of expect that a new instance of a multi_array could be created by passing a reference to anything that fullills he requirements of a multi_array. That seems not to be the case.
If you could pont me to any additional information on this library, I would be interested.
Robert Ramey
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