Hi, I've got an inner loop that I think I can see is strict in the Int argument being passed around, but that GHC 6.6.1 isn't unboxing. In the following example both functions take a GHC.Base.Int, which I think should be an Int#. Rec { f60_rS5 :: GHC.Prim.State# GHC.Prim.RealWorld -> GHC.Base.Int -> GHC.Base.Int [GlobalId] [Arity 2 NoCafRefs Str: DmdType LL] f60_rS5 = \ (v1_aWH :: GHC.Prim.State# GHC.Prim.RealWorld) (v2_aWI :: GHC.Base.Int) -> case $wccall_r2kv v1_aWH of wild_X2j { (# ds_d1V4, ds1_d1V3 #) -> case ds1_d1V3 of wild1_X2L { __DEFAULT -> f60_rS5 ds_d1V4 v2_aWI; (-1) -> v2_aWI; 10 -> f561_r2kx ds_d1V4 v2_aWI } } f561_r2kx :: GHC.Prim.State# GHC.Prim.RealWorld -> GHC.Base.Int -> GHC.Base.Int [GlobalId] [Arity 2 NoCafRefs Str: DmdType LL] f561_r2kx = \ (v1_aWm :: GHC.Prim.State# GHC.Prim.RealWorld) (v2_aWn :: GHC.Base.Int) -> case $wccall_r2kv v1_aWm of wild_X2j { (# ds_d1V4, ds1_d1V3 #) -> case ds1_d1V3 of wild1_X2P { __DEFAULT -> case v2_aWn of wild2_a2du { GHC.Base.I# x_a2dw -> case wild1_X2P of wild3_X35 { __DEFAULT -> f60_rS5 ds_d1V4 (GHC.Base.I# (GHC.Prim.+# x_a2dw 1)); 10 -> f561_r2kx ds_d1V4 (GHC.Base.I# (GHC.Prim.+# x_a2dw 1)) } }; (-1) -> v2_aWn } } end Rec } This code comes from a line counting program, I have attached the entire source. My character counting program does infer the correct strictness, although that is based on a single self-recursive function. The largest obvious difference is that the strictness depends on the two functions which call each other - does this impeed GHC's strictness analysis? Thanks Neil