My experience in math unfortunately is that code is just about unpublishable. I'd love to be able to just have relevant code in a paper, but editors will reject it.

They'll also reject you for having too much discussion and explanation. Now that almost all "papers" are PDFs and we don't have to worry about printing costs, I worry that the expected brevity in math is just elitism. Sure, if you're one of the six experts in the sub sub subfield the paper concerns itself with, the brevity is welcome, but for everyone else...