Hi, I'm trying to write an arrow for a real-time stream processor. I'm basing it on the SP type in Hughes paper on Generalising Monads to Arrows (http://www.cs.chalmers.se/~rjmh/Papers/arrows.pdf) section 6. I've extended this with a notion of time by making each step a function of time. But I can't get the compose operator to work. The arrow itself is defined in http://haskell.pastebin.com/m49944f64 with the (.) function highlighted. Some simple tests are in http://haskell.pastebin.com/m6d90f27 with the problematic call highlighted. When run it produces an infinite list of puts, which causes the SimulateRTSP interpreter function to diverge. But I've run the expansions by hand, and they seem to work (see the test case file at the bottom). I'm going nuts looking at this. Can anyone see what I'm doing wrong? Thanks, Paul.