Proposal: add fromRight and fromLeft to Data.Either

[Edward Kmett]

Putting on my CLC hat to summarize the talk so far into a concrete plan:

It looks like there is sufficient consensus to add the

fromLeft :: a -> Either a b -> a
fromRight :: b -> Either a b -> b

variants to Data.Either, so let's do that.

This avoids partiality concerns, and seems to have broad support. I'll
modify the `either` package to re-export them once they make it into base
to avoid import conflicts.

Does someone want to bang out a patch?

-Edward

On Sun, Jun 12, 2016 at 2:29 AM, Erik de Castro Lopo <mle+hs at mega-nerd.com>
wrote:

> Anton Felix Lorenzen wrote:
>
> > When working with Either,
> > I am often missing two simple functions:
> > fromRight :: Either a b -> b
> > fromLeft  :: Either a b -> a
> >
> > It has been implemented a couple of times:
> > http://hayoo.fh-wedel.de/?query=fromRight
> >
> > But I don't want to depend on yet another library
> > for such a basic function.
> >
> > Could it be added?
>
> -1 on the addition of yet another partial function.
>
> Erik
> --
> ----------------------------------------------------------------------
> Erik de Castro Lopo
> http://www.mega-nerd.com/
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