Hi Claus, I've had a look at this example in GHood, and you are right, nhc98 does seem to create several copies of v-in.
import Observe
foo1 m = take m (observe "v-out" v) where v = 1 : concat (map triple (observe "v-in" v)) triple x = [x,x,x]
main = printO $ (foo1 100::[Int])
Perhaps Malcolm can explain what nhc98 does with this example?
At a guess, I think the answer lies in lambda-lifting. nhc98 -c Leak.hs +CTS -lift -CTS shows this code for `v' (reformatted a little to make it easier to read): Main.Prelude.173.v = \ v223 v224 -> Prelude.: (Prelude._apply1 (Prelude.fromInteger v223) 1L) (Prelude._apply1 (Prelude.concat) (Prelude.map (Main.Prelude.174.triple) (Observe.observe (Observe.Observable.Prelude.[] v224) (LAMBDA225) (Prelude._apply2 (Main.Prelude.173.v) v223 v224)))) v takes two arguments; v223 represents the numeric dictionary, and v224 the Observer dictionary. The recursive reference to v is not a cyclic pointer to a constant structure, but actually a function call. I believe the real culprit is that nhc98 does not implement the monomorphism restriction. IIRC, the DMR applies to every group of simple pattern bindings at the same let-bound scope, not just the top-level, so really we ought to default-away the dictionaries, which would solve this particular space oddity. Regards, Malcolm