Help needed: Restrictions of proc-notation with RebindableSyntax

Richard Eisenberg rae at
Sat Dec 24 03:32:16 UTC 2016

To clarify my comments in this thread around desugaring: I was referring to the concrete Haskell code as written in GHC, not at all to an abstract desugaring algorithm. The implementation of arrows in GHC uses fixM, which is a nuisance. And I don't understand the code well enough to be able to untie the knot. I have a solid workaround for the time being, but it's indeed a workaround.


> On Dec 21, 2016, at 5:09 PM, Tom Ellis <tom-lists-haskell-cafe-2013 at> wrote:
> On Wed, Dec 21, 2016 at 01:49:33PM -0600, amindfv at wrote:
>> Additionally, Opaleye uses Arrow syntax pretty heavily iirc.
> If I were writing the Opaleye tutorial today (and if I rewrite it) I will
> shy away from arrows and encourage users to use applicative style.  There's
> only one operator where applicative is not enough, 'restrict', and that can
> be wrapped up as a different combinator so that no one knows they're ever
> using arrows.
> Tom
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