Haskell Platform Proposal: add transformers and revise the mtl package to depend on it

[Ross Paterson]

On Thu, Sep 16, 2010 at 11:10:37AM +0200, Johan Tibell wrote:
> I would like to know if this additional abstraction has a noticeable
> performance cost. Does anyone know of a benchmark that could be used to test
> this? Perhaps one involving State.

With mtl-1, the following

    incr1 :: State Int ()
    incr1 = do
            n <- get
            put $! n+1

    incr2 :: StateT Int Identity ()
    incr2 = do
            n <- get
            put $! n+1

generate the same Core code (except for casts).