[Haskell-cafe] Best practices for Arrows?

[Tom Ellis]

On Sat, Jun 22, 2013 at 10:24:23PM +0100, Ross Paterson wrote:
> On Sat, Jun 22, 2013 at 07:05:09PM +0100, Tom Ellis wrote:
> > On Sat, Jun 22, 2013 at 03:36:15PM +0200, Ertugrul Söylemez wrote:
> > > If the interface is not under your control, make yourself comfortable
> > > with the complete arrow syntax, most notably how it handles operators,
> > > combinators and the `(| banana bracket notation |)`.  This is very
> > > valuable information.
> > 
> > Interesting.  I hadn't noticed the `(| banana bracket notation |)` on the
> > GHC Arrows page[1] before, but just saw it when I went back to check.
> 
> The banana brackets can be handy when you have operations on your arrow
> type beyond the ones in Arrow and ArrowLoop.  But beware that the types of
> the operations you can use with it will be changing in the next release
> of GHC.  The change is the first one described on
> 
> http://hackage.haskell.org/trac/ghc/wiki/ArrowNotation

Is there any example of using Arrow banana brackets?  I downloaded all of
Hackage and grepped it, and the only usage was in the comments of
Control.Arrow.Internals!

I have feeling these might be useful to me, but I can't quite understand how
they work.

Tom