Hi, I am experimenting with rewrite rules, but found that they do not fire as often as I wanted them. Here is a small example: module MapId where myMap f [] = [] myMap f (x:xs) = f x : myMap f xs {-# RULES "map id" myMap id = id #-} {-# RULES "map id2" myMap (\x -> x) = id #-} mapId = myMap id mapIdApp x = myMap id x mapLamId = myMap (\x -> x) mapLamIdApp x = myMap (\x -> x) x This works as expected, i.e. the latter four functions become some kind of identity. But I am a bit surprised that I do need two rules to catch all cases, as I thought that the simplifier „looks through“ definitions like "id". But when I remove the "map id" rule, the functions "mapId" and "mapIdApp" are not optimized. So I wonder: Why is rule "map id2" not enough here? Thanks, Joachim -- Joachim "nomeata" Breitner mail@joachim-breitner.de | nomeata@debian.org | GPG: 0x4743206C xmpp: nomeata@joachim-breitner.de | http://www.joachim-breitner.de/