[Haskell-cafe] mixing map and mapM ?

[Pierre-Etienne Meunier]

This way :

do
	times<-mapM PF.getFileStatus filenames >>= return.(map PF.modificationTime)

Or also :

do
	times<-mapM (PF.getFileStatus >>= (return.(PF.modificationTime))) filenames
	let sorted=...

I do not know exactly how ghc compiles the IO monad, but it seems to me that the latter would allocate a little less.

Cheers,
PE

El 06/05/2010, a las 01:01, <briand at aracnet.com> <briand at aracnet.com> escribió:

> 
> I was doing the following:
> 
> 
> do status <- mapM PF.getFileStatus filenames
>   let times = map PF.modificationTime status
>   let sorted = sortBy (\(_, t1) (_,t2) -> compare t1 t2) (zip filenames times)
> 
> and I thought, surely I can combine the status and times definitions into one line, only I can't.
> 
> Hint ?
> 
> Thanks,
> 
> Brian
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