[Haskell-cafe] Re: Is StateT what I need?
g9ks157k at acme.softbase.org
Mon Dec 17 15:40:28 EST 2007
Am Montag, 17. Dezember 2007 21:06 schrieb ChrisK:
> Andre Nathan wrote:
> > Hello (Newbie question ahead :
> > I tried this for insertProc, but it obviously doesn't work... what would
> > be the correct way to do this?
> >> insertProc :: Pid -> StateT PsMap IO PsInfo
> >> insertProc pid = do
> >> proc <- procInfo pid -- XXX this is obviously wrong...
> >> psMap <- get
> >> put (Map.insert pid proc psMap)
> >> return (proc)
> I see that using "lift" makes it compile (Control.Monad.Trans.lift):
> > insertProc pid = do
> > proc <- lift (procInfo pid)
By the way, be careful with identifiers named “proc”. There is a syntax
extension (arrow notation) which introduces a new keyword “proc”.
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