David Menendez wrote:
Neat! Are you getting this from -ddump-simpl?
Yep, that's the most readable intermediate form to look at IMHO.
[...] helper2 = \ds eta -> case ds of (n,a) -> ( case eta of (x,y) -> x `plusInt` y , case eta of (x,y) -> y ) [...] I don't know what to make of that. Semantically, helper2 is identical to helper, but I'm not brave enough to look at the C output to see if they produce different results.
Well, they are almost equivalent: If you keep the second element of the result of helper2 alive without having it evaluated, you keep the first element of the second argument of helper2 alive, too. Depending on the usage of helper2, this might make a difference in the space behaviour, but in our current example it doesn't matter very much. If in doubt, use e.g. GHC's profiling facility, which can produce nice & colourful graphs, useful for impressing your friends... :-) Cheers, S.