Newbie qustion about monads

[Juanma Barranquero]

On Thu, 2 Oct 2003 12:30:54 +0100
Alastair Reid <alastair at reid-consulting-uk.ltd.uk> wrote:

> Observational equivalence.
> 
> For monads like list and maybe, this boils down to the normal equality because 
> the standard equality on these types is exactly observational equality.
> 
> For monads like IO, you can't define an Eq instance so it comes down to what 
> can the user of the program observe.

OK.

But in my examples, the difference is observable only if I do define a
"count" or equivalent to show it. Otherwise, c1/c2 (or m1/m2) are
indistinguishable.

> (There's a little circularity there and I'm ignoring the exception part of 
> parser monads but, hopefully, you get the idea.)

Yes, thanks a lot.

                                                                Juanma