http://awwx.ws/mpair0 was my attempt to simply modify Arc 3.1's ac.scm to use mpair's. I got enough working to see that using mpair's appeared to fix the queue bug, but my implementation was otherwise quite buggy. (Lots of places where Racket lists appeared where Arc lists should have been, and vice versa; and weird mixes of the two, etc.) I have no doubt that someone cleverer than me could get it to work, but I just kept getting lost trying to figure out my bugs.
So I decided to implement the compiler incrementally, where I could test each step as I went. It would take a lot more work (a bit like getting my jeep stuck in the swamp, and so hauling myself out ten feet at a time with a winch), but it was an approach that I knew I would be successful at.
Then, since I was rolling through a compiler rewrite anyway, I decided to also go ahead and reflect the compiler into Arc to make it more hackable ^_^.
