Vesa Karvonen posted a complete solution in SML here[1] (but LtU seems to be down so the link doesn't work), which I transliterated (directly, not idiomatically

Vesa Karvonen posted a complete solution in SML here[1] (but LtU seems to be down so the link doesn't work), which I transliterated (directly, not idiomatically) to F# here[2]. [1] http://lambda-the-ultimate.org/node/2232#comment-31278 http://lambda-the-ultimate.org/node/2232#comment-31278 [2] http://fssnip.net/gn http://fssnip.net/gn