[Haskell-cafe] arrow notation

[Conal Elliott]

On Thu, Feb 7, 2013 at 5:41 PM, Ross Paterson <ross at soi.city.ac.uk> wrote:

> On Thu, Feb 07, 2013 at 02:49:40PM -0800, Conal Elliott wrote:
> > I make some use of arrow notation, though sadly I often have to avoid
> > it because my (pseudo-)"arrows" don't have arr. I'd love to see a
> > variant that has restricted expressiveness in exchange for arr-freeness.
>
> It's hard to imagine arrow notation without arr (or at least
> contravariance in the first argument of the "arrow") because forming
> expressions using the local environment is so central to it.  That is,
> I can't imagine what things you are trying to write in that situation.
>

What I have in mind is a small collection of methods including fst & snd
(and similarly for sums) that could be defined via arr but could instead
form the basis of translating restricted arrow notation for (pseudo-)arrows
that don't support arr.

I keep running into these pseudo-arrows in practical work. The reliance of
arrow notation on arr means that I can't use arrow notation, and my code is
terribly difficult to read.

-- Conal
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