puzzlecad-examples error

[Hickname]

In puzzlecad-examples.scad in the box section we have following example:

// packing_box is also useful for modeling certain obstructed tray puzzles, by setting $burr_scale
// to a vector. Here's the tray from Coffin's Fourteen Steps. Notice how $box_wall_thickness and
// $box_inset are also vectors, in order to provide fine-grained control over the dimensions and
// tolerances.
*packing_box([
    "xxxxxxx|xxxxxxx|xxxxxxx|xxxxxxx|xxxxxxx|xxxxxxx|xxxxxxx",
    "xxxxxxx|x.....x|x.....x|x.....x|x.....x|x.....x|xxxxxxx",
    "xxxxxxx|x++...x|x+++..x|x+++..x|x+++++x|x+++++x|xxxxxxx"
], $burr_scale = [16, 16, 5.6], $box_wall_thickness = [8, 8, 3],
   $box_inset = [0.07, 0.07, 0.3], $plate_width = 200, $auto_layout = true);

It gives the following error: [ERROR: Assertion 'is_num($burr_inset)' failed: "$burr_inset must be a scalar." in file puzzlecad/puzzlecad-burr.scad, line 154]

[wesleyanderson]

I am new to puzzlecad, and I only have a little experience with scad, but I've been a professional developer for a couple decades, so I thought I would dig into this a bit. Hopefully this will help resolve this issue or at least provide a workaround for others trying to get the examples to work.

The following might be a workaround, at least for the examples.
Including $box_cutout_inset = 0.07 as a parameter on the packing_box call in puzzlecad-examples.scad (see below), makes the example run successfully. I do not know if this is useful in practice (i.e. in a puzzle model that you want to 3D-print), or if it just makes the example work.
packing_box([ "xxxxxxx|xxxxxxx|xxxxxxx|xxxxxxx|xxxxxxx|xxxxxxx|xxxxxxx", "xxxxxxx|x.....x|x.....x|x.....x|x.....x|x.....x|xxxxxxx", "xxxxxxx|x++...x|x+++..x|x+++..x|x+++++x|x+++++x|xxxxxxx" ], $burr_scale = [16, 16, 5.6], $box_wall_thickness = [8, 8, 3], $box_inset = [0.07, 0.07, 0.3], $box_cutout_inset = 0.07, $plate_width = 200, $auto_layout = true);

TLDR:
This was my analysis.

Following the stack-trace, in puzzlecad-boxes.scad (line 351) I see
burr_piece_base(burr_info, $burr_inset = is_undef($box_cutout_inset) ? $box_inset : $box_cutout_inset);

And from the puzzlecad-examples.scad (line 495-500)
packing_box([ "xxxxxxx|xxxxxxx|xxxxxxx|xxxxxxx|xxxxxxx|xxxxxxx|xxxxxxx", "xxxxxxx|x.....x|x.....x|x.....x|x.....x|x.....x|xxxxxxx", "xxxxxxx|x++...x|x+++..x|x+++..x|x+++++x|x+++++x|xxxxxxx" ], $burr_scale = [16, 16, 5.6], $box_wall_thickness = [8, 8, 3], $box_inset = [0.07, 0.07, 0.3], $plate_width = 200, $auto_layout = true);

In puzzlecad-examples.scad, the $box_inset is described as a vector, and that is the only way it is used in the examples. I see that $box_cutout_inset is set to undef (in puzzlecad.scad, line 55), and since $box_inset is a vector, it looks like $burr_inset is being set to a vector, which is not the scalar that burr_piece_base requires.

If I change line 351 in puzzlecad-boxes.scad to use the first element in $box_inset (see below), then it also does not fail, but that is unlikely to be a correct fix. All that change does is confirm that $box_inset is being used for that example and that it is a vector as expected.
burr_piece_base(burr_info, $burr_inset = is_undef($box_cutout_inset) ? $box_inset[0] : $box_cutout_inset);

I don't see anything describing $box_cutout_inset in puzzlecad-examples.scad, but the only other place I see it used in puzzlecad-boxes.scad it is passed to vectorize, so it looks like it should be (or at least can be) a scalar.

As noted above, if I include $box_cutout_inset = 0.07 in the packing_box call in puzzlecad-examples.scad, then it does not fail. It is not clear to me, though whether $box_cutout_inset is intended to be used that way or what a good default value would be (zero gives warnings) or what a correct fix would be. If I get time to dig in and understand this project better I will try to submit a pull request. I appreciate all of the work that has gone into producing this project, and I would be happy to help if I can.