generalization of maybeToList

[Brent Yorgey]

On Tue, Feb 14, 2012 at 03:36:22PM -0500, Edward Kmett wrote:
> The biggest problem is that with each one of these being so short and with
> so many useful variations, the concepts struggle to cross the "Fairbairn
> threshold".

What is the "Fairbairn threshold"?  I tried doing a Google search for
it, and all I got was a bunch of messages from libraries at haskell.org
(all of which only *referenced* it, without defining it).

-Brent

> 
> On Tue, Feb 14, 2012 at 10:47 AM, Jeff Shaw <shawjef3 at msu.edu> wrote:
> 
> > I'm all for generalizations! I have a second, very similar function I
> > think should be added, but I don't have a good name for it.
> >
> > maybe mzero id :: MonadPlus m => Maybe (m a) -> m a
> >
> > Perhaps there is once again an equivalent for Alternative.
> >
> >
> > On 2/14/2012 10:24 AM, Edward Kmett wrote:
> >
> >> If you are going to add one then the generalization of your
> >> generalization to Alternative might be better.
> >>
> >> maybeA = maybe empty pure
> >>
> >> On Feb 14, 2012, at 9:55 AM, Jeff Shaw<shawjef3 at msu.edu>  wrote:
> >>
> >>  I find myself using this function quite a lot. I believe it should be
> >>> included in Data.Maybe.
> >>>
> >>> import Control.Monad
> >>>
> >>> maybeTo :: (MonadPlus m) =>  Maybe a ->  m a
> >>> maybeTo =
> >>>    maybe mzero return
> >>>
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> >

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