Tue, 20 Feb 2001 17:52:33 -0800, Konst Sushenko <[EMAIL PROTECTED]> pisze:
> lookahead p = do { s <- fetch
> ; lift (evalState p s)
> }
>
> is typed as
>
> lookahead:: State MyState Maybe a -> State MyState Maybe (a,MyState)
>
> but i need
>
> lookahead:: State MyState Maybe a -> State MyState Maybe a
myEvalState = liftM fst yourEvalState
Andy Gill's monadic modules provide evalState as a wrapper for runState,
which throws away the state component returned.
--
__("< Marcin Kowalczyk * [EMAIL PROTECTED] http://qrczak.ids.net.pl/
\__/
^^ SYGNATURA ZASTÊPCZA
QRCZAK
_______________________________________________
Haskell-Cafe mailing list
[EMAIL PROTECTED]
http://www.haskell.org/mailman/listinfo/haskell-cafe
