[Haskell-cafe] Alternative versus Monoid

[Yves Parès]

 "1) What about the First type? Do we {-# DEPRECATE #-} it?"

Personnaly, I'm in favor of following the same logic than Int:
Int itself is *not *a monoid. You have to be specific: it's either Sum or
Mult.

It should be the same for Maybe: we remove its instance of Monoid, and we
only use First and Last.

2011/12/16 Bas van Dijk <v.dijk.bas at gmail.com>

> On 16 December 2011 05:26, Brent Yorgey <byorgey at seas.upenn.edu> wrote:
> > I, for one, would be
> > quite in favor of changing the current Monoid (Maybe a) instance to
> > correspond to the failure-and-prioritized-choice semantics
>
> So lets do this. Some questions:
>
> 1) What about the First type? Do we {-# DEPRECATE #-} it?
>
> 2) What about the Last type? It could be deprecated in favor of Dual.
>
> 3) Do we need a new type (like the current Maybe) for lifting
> semigroups into a Monoid? IMHO we don't since the semigroup package
> does a better job with the Option type (like Brent mentioned).
>
> 4) How much code will break from this change?
>
> 5) Anyone up for proposing this to libraries at haskell.org?
>
> Regards,
>
> Bas
>
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