[Haskell-cafe] ANN: HLint 1.2

[Bas van Dijk]

On Mon, Jan 12, 2009 at 6:47 PM, Max Bolingbroke
<batterseapower at hotmail.com> wrote:
> GHC should indeed be doing so. I'm working (on and off) to work out
> some suitable heuristics and put the transformation into ghc -O2.
> There are a few wrinkles that still need sorting out, but preliminary
> indications are that it decreases the runtime of our standard
> benchmark suite, nofib, by 12% or so.

Great!

In the Stream library I'm developing at http://code.haskell.org/Stream
I 'closurize' (for lack of a better name) all my functions. Here are a
few random examples:

repeat :: a -> Stream a
repeat x = repeat_x
    where
      repeat_x = x ::: repeat_x

cycle :: [a] -> Stream a
cycle xs = cycle_xs
    where
      cycle_xs = foldr (:::) cycle_xs xs

deleteBy :: (a -> a -> Bool) -> a -> Stream a -> Stream a
deleteBy eq x = deleteBy_eq_x
    where
      deleteBy_eq_x (y ::: ys)
          | eq x y    = ys
          | otherwise = y ::: deleteBy_eq_x ys

Closurizing the functions in Data.Stream lead to 10% to 250% speedups!

Note that I follow a particular naming convention for the inner worker
functions. I use the top level function name and append the
'closurized' arguments to it interspersed with underscores.

regards,

Bas