dist_fast :: UArr Double -> UArr Double -> Double dist_fast p1 p2 = sumDs `seq` sqrt sumDs where sumDs = sumU ds ds = zipWithU euclidean p1 p2 euclidean x y = d*d where d = x-y
You'll probably want to make sure that 'euclidian' is specialized to the types you need (here 'Double'), not used overloaded for 'Num a=>a' (check -ddump-tc, or -ddump-simpl output).
Sorry about that misdirection - as it happened, I was looking at the tc output for 'dist_fast' (euclidean :: forall a. (Num a) => a -> a -> a), but the simpl output for 'dist_fast_inline' .., which uses things like __inline_me .. case Dist.sumU (Dist.$wzipWithU .. GHC.Num.- @ GHC.Types.Double GHC.Float.$f9 x_aLt y_aLv Once I actually add a 'dist_fast_inline_caller', that indirection disappears in the inlined code, just as it does for dist_fast itself. dist_fast_inlined_caller :: UArr Double -> UArr Double -> Bool dist_fast_inlined_caller p1 p2 = dist_fast_inlined p1 p2 > 2 However, in the simpl output for 'dist_fast_inline_caller', the 'sumU' and 'zipWithU' still don't seem to be fused - Don? Claus