[bbkane]

I know Go is justly criticized for many of its design decisions, but it still feels well-designed and "small" to me in day to day usage when many other languages don't.

[a-french-anon]

Eh, the thing with generics coming late is pretty much what I meant by "organically grown".

My best litmus test these days is support for multidimensional arrays because it's always needed at some point in general purpose languages. CL and Ada had it right from the start while C++ needed C++23/26 to get std::mdspan and we still need to wrap it to pass the underlying/owned memory pool around (https://rosettacode.org/wiki/Multi-dimensional_array for more).

[nish__]

Doesn't every language support multidimensional arrays? It's just an array of arrays, no? What am I missing?

[umanwizard]

An array of arrays is an extremely inefficient and error-prone way to represent multidimensional arrays.

If I want a 1000x1000 array, representing it physically as a single 1000000-element array requires one allocation, and processing it element-by-element (assuming it's stored in the same order we're iterating over it) is sequential in memory and therefore very efficient.

Representing it as 1000 separate 1000-element arrays requires 1000 allocations, and pointer-chasing every time we move from one row to the next.

[j_w]

Isn't an array of arrays by definition the sequential implementation?

Otherwise you would have an array of pointers to arrays. The usage (syntax) for them would be the same but the performance would not be.

They also have different uses. You would expect an array of arrays to be an array of arrays which share the same length. For an array of pointers to an array you would expect dynamic length arrays contained within the original array.

Even in c++ could you not just define some int [1000][1000]foo? I've never really used C++ but my C knowledge assumption is that is 1000000 continuous elements.

[20k]

The C++ way to do it currently would be:

    std::array<std::array<T, N>, M> data;

Which is contiguous

    int data[M][N]; 

also works fine and is contiguous in C++

Edit:

For the stack at least. On the heap, you'd need to use a single std::vector<int> and do the indices manually, or use mdspan

[uecker]

I does not work fine in C++ when N and M are not compile-time constants, which is basically always the case in any interesting numerical algorithm. Also not in Rust.

It works fine in C though, or FORTRAN, or Ada, or ALGOL 60, ...

[shakow]

> Even in c++ could you not just define some int [1000][1000]foo?

If it fits on the stack, yes.

Typical code using MD-arrays is scientific code, and the data they manipulate generally do not fit there.

[j_w]

Would the compiler not allocate the memory contiguously on the heap in that case then? Seems like a reasonable thing to do.

[nish__]

I see. That makes sense.