I banged out a little something at <https://github.com/CTMacUser/ArrayMD>. The "boost::container::array_md<T, N>" class template can be used like the (C++11) std::array. It has the same members (value_type, size_type, difference_type, reference, const_reference, pointer, const_pointer, iterator, const_iterator, reverse_iterator, const_reverse_iterator, at, front, back, operator[], data, begin, cbegin, end, cend, rbegin, crbegin, rend, crend, empty, size, max_size, fill, and swap). It has external functions operator==, operator!=, and swap. It fulfills the Container and Reversible-Container archetypes, with random-access iterators. It lacks: * support for 0 as the length. It combines the type and extent directly as the internal array's type expression, so the compiler will complain if zero-length arrays are used. (You also can't use a function type, reference, or class-type that's marked abstract as element types.) But front, back, and data will always be valid. * The ordered-comparison operators (<, >, <=, and >=). * The get access function, plus helper specializations for std::tuple_size and std::tuple_element. It adds: * 3 class-static constants: dimensionality (= 1), static_size (= N), and static_sizes (a one-element array with value N). * 2 type aliases: direct_element_type (= value_type) and data_type (= direct_element_type[N]). * If value_type is an array type, fill still works, by doing assignments at the inner non-array level. * The apply member functions, that call a function over each element, including the element and its index coordinate with each call. * operator(), which works just like operator[]. * As many member functions work with constexpr and/or noexcept as possible. Array_md is an aggregate type. It is trivially-copyable, trivial, standard-layout, and/or POD if the element type is. It has default-, copy-, move-construction, destruction, copy-, and/or move-assignment if the element type does. (Default-initialization follows the element type's lead if its code-ful or random garbage bits.) Initialize it like a structure with a single member object of type data_type. Indicated by the "md" suffix, the array modeled by this class template can be multi-dimensional. Unlike C-level arrays, which are all nested one-level arrays, this class template lets you express multi-dimensionality flatly. And the arguments are compatible with the comma-separated lists used in variadic stuff. When you add another extent M (BEFORE the others): * ++dimensionality * static_size *= M * static_sizes -> { old static_sizes, M } * direct_element_type = old data_type * data_type = direct_element_type[ M ] * The apply method sends the remote function each element along with all of its index coordinates (dimensionality + 1 arguments total). * operator[] still takes one argument, and returns a direct_element_type&. You can continue to chain-index to the element type just like nested built-in arrays. * operator() and at can take as many arguments as dimensionality. Using that many indices gives an element, using less gives a reference to an intermediate array (which you can use the built-in operator[] on). If you use no indices, then you get a reference to the entire implementation C-level array returned. (I originally had operator() put in since operator[] can't handle multiple direct arguments.) You can crank the recursion backwards, and have an array with no extents. Such a type supports one element (NOT zero, since one is the multiplicative identity). That's another reason not to special-case zero-value extents in, to keep the size non-decreasing with new extents. This degenerate case doesn't support static_sizes (since it would be an illegal zero-length array) or operator[] (since there's no array member object). Added late to the cycle: When perusing the C++11 standard, I noticed that operator[] can take a std::initializer_list argument, although the core language never uses it; it's only for UDTs. I added support for that. I added support for it in the operator() and at methods, for symmetry. The length of the list must equal dimensionality. To-do: Should I implement get, tuple_size, tuple_element, and the ordered-comparison operators? They're very linear-oriented. I'm not sure they're used that much. And I'm not sure what they would even mean for a non-linear container; I may have to apply some sloppy linearity for them to be defined. (I don't think I could make them (get, tuple_size, and tuple_element) multi-coordinate; then they couldn't work with generic code.) I was trying to avoid any linearity, and depend on apply for iteration-related tasks. Then I decided to support the range-for statement. Then it looked weird to have a sloppy & minimal begin/end tacked on, so I put in a full iteration set. Then at that point, I put in so many things like std::array that I put everything else in so they could have source compatibility. (BTW, there are several utility/helper classes and functions. Some are in separate headers, the others near the start of "array_md.hpp".) Versus Boost.MultiArray: (This is from a quick look at BMA.) BMA statically declares the element type and the number of dimensions; the actual extent values (and therefore the element count) and the elements themselves are determined/allocated at run-time. It's like std::vector vs. std::array, the former is more powerful, but may be overkill that limits compile-time opportunities, while the latter can take advantage of compile-time optimizations and can shift memory usage from the heap to the stack. Versus Brian J Smith's Array (at <https://github.com/BrianJSmith/Array>), on the review queue: * (Used to support extent values of 0, but has been removed). * Requires at least one extent, while array_md supports 0 extents. * Implements multi-dimensions as maps::array objects nesting each other, similar to how C-level arrays are made multi-dimensional. The array_md model computes the nested C-level array type and stores that directly. This has big consequences, because of padding. Class types may add padding bytes before(?), between, and after their non-static member data sub-objects. Built-in array types never have padding. So maps::array may end up with lots of padding bytes scattered through it, while array_md has one set of padding and its elements contiguous. This makes implementing the data method possible; it can't work with maps::array unless we get lucky and the compiler doesn't add any padding. (The data method isn't provided by maps::array anyway; the "data" name is used differently.) * Due to the above, maps::array matches nested C-level arrays in that range-for iterates over the immediately-lower level of elements. This is OK when dimensionality is 1, but higher dimensions can't dig into the element type through range-for. The array_md class's range-for support is at the element level, due to being able to define the data method. * There are operators * (unary) and + (binary) overloads. They seem more for iterators than containers; then I figured out that he's simulating the effects of array-to-pointer conversions, which make these operations possible. That decay action is something we shouldn't be exalting. (And there isn't a reversed version for offset + container.) * There's no option to input all the indices at once for "at," instead maps::array needs to chain them. (There's no throw-less version called operator(), needed due to operator[] being limited to one argument.) (There's no initializer-list variants either; but the maps::array code has no C++11 features besides variadic templates.) * There is stream-output code. * There is ordered-relations operator (< > <= >=) code. * Revealing the values for the dimensions outside of the template header differ. * Actually has documentation, as opposed to Doxygen comments. Daryle W.