Changes performed on vacation in Austria

I changed quite a bit about the pts interpreter while on vacation (not so much from work, but certainly from the internet). Most importantly, see f4c65a0a88b5a978b0c17fdec54b703062b4bcfb and 3d3be1db5fcdee2171466808c38df524fbf1287c.

Not sure what to do about this. I'm not super motivated to split it up into multiple pull requests.