On 08/16/2011 09:23 AM, Stephen Tetley wrote:
> {-
> I don't think parametric monads will solve your problem though, as you
> want a product of the states as the result of bind. Are you really
> sure you want this behavior?, I'd imagine it breaks the monad laws
> anyway.
> -}
It seems that the pr
You can't define (>>=) if your state type changes:
(>>=) :: m a -> (a -> m b) -> m c
Whereas, your bind is effectively three different parametric types:
_bind :: m1 a -> (a -> m2 b) -> m3 b
You can use parametric monads to represent state changing within a
monad. Oleg Kiselyov has tutorials on
Dear Cafe,
I'm building an abstraction for representing sequences as difference
equations, storing initial values and update equation.
I have something that resembles a Monad, but has an extra state
parameter s that "grows" on _join or _bind, so I can't simply create
an instance Monad (Sig s).
