Apparently you can make it work with posns by requiring lang/posn and then using the pattern: (struct posn-id (x y)) You could probably make your own teachpack that reprovided both match and renamed posn-id back to posn, unless you are using Signatures. Robby On Wednesday, August 17, 2011, Prabhakar Ragde <<a href="mailto:plragde@uwaterloo.ca">plragde@uwaterloo.ca</a>> wrote: > On 8/17/11 6:02 PM, Robby Findler wrote: >> >> Could you just require match into bsl/isl? > > I had problems with BSL at some point, I think, but it hardly matters, there's no point in doing it before BSL+, where it does work, except not with posns. Which I don't think I'll use with my students in the fall, but I can't guarantee that none of them will fall into that relatively minor pit. (If it were up to me, I would take the built-in definition of posns out. I don't think being able to use `make-posn' for a few minutes before introducing `define-struct' is worth the hassle.) --PR >