On Wed, Mar 31, 2010 at 11:06 AM, Paul Brauner
data Term = Lam Term | App Term Term | Var Int
instance NFData where rnf (Lam t) = rnf t rnf (App t1 t2) = rnf t1 `seq` rnf t2 rnf (Var x) = rnf x
the actual datatype doesn't have fancy stuff like higher-order types for constructors, it's really similar. The only difference is that it is a GADT, but this souldn't change anything right?
Did I make some mistake in instancing NFData ?
No, your NFData instance is correct. You first pattern match on the term followed by recursively calling rnf on the sub-terms. This will correctly force the entire term. Maybe you could try using criterion[1] for your benchmark and see if that makes any difference. Something like: {-# LANGUAGE BangPatterns #-} import Criterion.Main main :: IO () main = let !t = genterm in defaultMain [bench "subst" $ nf (subst u) t] regards, Bas [1] http://hackage.haskell.org/package/criterion