list of results monad
Marcin 'Qrczak' Kowalczyk
12 Mar 2001 14:08:50 GMT
Mon, 12 Mar 2001 02:28:11 +0100, Hannah Schroeter <firstname.lastname@example.org> pisze:
> I *did* do a result monad once (for data compression, in fact
> the monad was combined for "imperatively" consuming input as well
> as "imperatively" producing output).
These monads are present in ghc >= 4.06, in -package lang, modules:
The combination of state and output can be done as one of these:
WriterT w (State s)
StateT s (Writer w)
RWS () w s
where w is the type of output and must be a monoid (e.g. a list)
and s is the type of state.
> data ResultM r a = RM (r -> (r,a))
This is isomorphic to MonadState.State.
__("< Marcin Kowalczyk * email@example.com http://qrczak.ids.net.pl/
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