Hi, for those of you who don’t follow Planet Haskell and haven’t seen my blog post¹ on it: I have created a (very) small library list-fusion-probe with an identity function fuseThis :: [a] -> [a] that will complain loudly (at run-time, for the time being) if the argument is not fused away. Using it might give you more confidence in that your code really fuses as well as you think it does. Greetings from TFP (where the invited talk by Geoffrey Mainland inspired me to write that), Joachim ¹ http://www.joachim-breitner.de/blog/archives/649-Does-list-fusion-work.html -- Joachim “nomeata” Breitner mail@joachim-breitner.de • http://www.joachim-breitner.de/ Jabber: nomeata@joachim-breitner.de • GPG-Key: 0xF0FBF51F Debian Developer: nomeata@debian.org