Is it possible to interleave two arrays/lists in Openscad

Question

I have 2 arrays and I'd like to interleave their values.

For example

Interleave([[1,2],[2,2],[3,2]], [[3,1],[4,1],[5,1]]);  // Should yield [[1,2],[3,1],[2,2],[4,1],[3,2],[5,1]]

However I can't get something like this to work.

function Interleave(Set1,Set2) =[for(x=[0:len(Set1)-1]) Set1[x], Set2[x]];

Answer 1

The comma is not doing what you expect. It's separating 2 list entries, the first one is the for generatator and the 2nd one is just Set2[x] which is undefined as the x belongs to the for.

You can see what's going on when using just a string for the second part:

function Interleave(Set1,Set2) =[for(x=[0:len(Set1)-1]) Set1[x], "test"];
// ECHO: [[1, 2], [2, 2], [3, 2], "test"]

To get the interleaved result, you can generate a list with 2 entries for each interation and unwrap that using each

function Interleave(Set1,Set2) =[for(x=[0:1:len(Set1)-1]) each [Set1[x], Set2[x]]];

Also note the ..:1:.. step size, this ensures sane behavior in case Set1 is empty. The start:end range behaves differently for backward compatibility reasons.