On Nov 23, 1:15 pm, Konrad Hinsen <[EMAIL PROTECTED]> wrote:
> On 21.11.2008, at 20:10, Adam Jones wrote:
>
> >> The file contains the macro definitions, the definitions of three
> >> popular monads (maybe, list, state), and some illustrations of their
> >> use. Comments are welcome!
>
> > Since they support mzero and mplus, aren't these equivalent to
> > Haskell's MonadPlus? (i.e. they're a little more than *just* monads)
>
> You can define :plus and :zero if they are appropriate for a monad.
> If they are defined, you can use them. None of the predefined monad
> machinery will use them at the moment, but I plan to implement
> conditions, which work only if :zero is defined.
>
> In Haskell there are two different types of monads because of the
> type system, but the Clojure implementation doesn't use the type
> system at all, so :plus and :zero are simply used by convention.
>
> > I've been kicking around the idea of re-implementing Haskell
> > typeclasses on top of multimethods. Now that I think more about it,
> > this probably wouldn't be much work.
>
> You need to find a way to store the type information with the data.
> That is easy if you limit yourself to a specific data structure, say
> a map with a key reserved for type information. But if you want to be
> able to use typeclasses for general Clojure data (e.g. make sequences
> an instance of Monad), I don't see a simple way to do it.
That's the problem I've been thinking on. I'm looking for a decently
sane way to build on the multimethod dispatch system here instead of
explicitly relying on types. The concept probably doesn't work very
well without a guaranteed unique method of identifying an object, like
a data type.
-Adam
>
> Konrad.
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