C++ static multi array wrapper

Question

Old c-style static arrays can be quite bothersome when passed as arguments, or returned as value. For that, the new std::array is quite convenient.

However for multi-array, there is nothing in std:: and the boost::multi_array isn't just statically allocated.

Of course, I could do, say,

std::array<std::array<int,3>,2> my_array;

but I find sligthly long and it corresponds to the inverted built-in declaration

int my_array[2][3];

I am just wondering if there is already some "library" coding such a concept (bi-dimensional or any-dimensional)

(which for the latter, if I am correct, must use some variadic template for typing e.g.

multi_array<int,3,4> A;
multi_array<int,3,5,8> B;
multi_array<int,4,7,8,9,8,3> C; //this one being quite rare though

)

EDIT : sorry about the first post, I didn't test

"but then my_array[1][2] is not the same as in (...)" What do you mean? It is the same. — R. Martinho Fernandes
– R. Martinho Fernandes, Commented Sep 8, 2012 at 16:36
Yes I am sorry about that, I just was absolutely sure but didn't test (I know, I know..., it's bad) — Bérenger
– Bérenger, Commented Sep 8, 2012 at 16:58

David Grayson · Accepted Answer · 2012-09-08 17:36:07Z

0

It might be overkill for your application, but I have worked with the Eigen library and think it's family of Matrix template classes might work for you. An example:

Eigen::Matrix<float, 3, 2> a;
a(1,0) = 1.1;
a(0,1) = 17.5;

EDIT 1: Oops, I don't know for sure if it supports N-dimensional matrices. But for 2-dimensional ones I know it is good.

I think you can use typedefs, either with Eigen or with std::array, to make your types more readable.

answered Sep 8, 2012 at 17:36

David Grayson

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1 Comment

Bérenger Over a year ago

Thanks. I also think it's also too much for just an array without particular mathematical meaning. I am also doing linear algebra so this library could be useful however

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