[Haskell-cafe] ANN: HLint 1.2

[Henning Thielemann]

On Mon, 12 Jan 2009, Duncan Coutts wrote:

> On Mon, 2009-01-12 at 01:02 +0100, Lennart Augustsson wrote:
>> Does GHC specialize map?  If it doesn't, then hand crafted version
>> could be faster.
>
> No because the current definition are recursive and ghc cannot inline
> recursive functions.
>
> map :: (a -> b) -> [a] -> [b]
> map _ []     = []
> map f (x:xs) = f x : map f xs
>
> It has to be manually transformed into a version that is not recursive
> at the top level:
>
> map :: (a -> b) -> [a] -> [b]
> map f = go
>  where
>    go []     = []
>    go (x:xs) = f x : go xs
>
> Then the map can be inlined at the call site and the 'f' inlined into
> the body of 'go'.

Maybe HLint can make such suggestions ...