Comment by geocar

Off by one issues are also an argument given in favour of no indexing.

    groups=new Array(3).fill([])
    items.reduce(function(a,x,y){y=a.shift();y.push(x);a.push(y);return a},groups)

Array languages typically have a reshaping operator so that you can just do something like:

    groups:3 0N#items

Does that seem so strange? 0N is just null. numpy has ...reshape([3,-1]) which wouldn't be so bad in a hypothetical numjs or numlu; I think null is better, so surely this would be nice:

    groups = table.reshape(items,{3,nil})   -- numlu?
    groups = items.reshape([3,null])        // numjs?

Such a function could hide an ugly iteration if it were performant to do so. No reason for the programmer to see it every day. Working at rank is better.

On the other hand, Erlang is also 1-based, and there's no numerl I know of, so I might write:

    f(N,Items) -> f_(erlang:make_tuple(N,[]),Items,0,N).
    f_(Groups,[],_,_N) -> Groups;
    f_(G,Items,0,N) -> f_(G,Items,N,N);
    f_(G,[X|XS],I,N) -> f_(setelement(I,G,X),XS,I-1,N).

I don't think that's too bad either, and it seems straightforward to translate to lua. Working backwards maybe makes the 1-based indexing a little more natural.

    n = 0
    for i = 1,#items do
      if n < 1 then n = #groups end
      table.insert(groups[n],items[i])
      n = n - 1
    end

Does that seem right? I don't program in lua very much these days, but the ugly thing to me is the for-loop and how much typing it is (a complaint I also have about Erlang), not the one-based nature of the index I have in exactly one place in the program.

The cool thing about one-based indexes is that 0 meaningfully represents the position before the first element or not-an-element. If you use zero-based indexes, you're forced to either use -1 which precludes its use for referring to the end of the list, or null which isn't great for complicated reasons. There are other mathematical reasons for preferring 1-based indexes, but I don't think they're as cool as that.