Thomas, I'd be very careful mixing effectful arrows with the CCA framework. Effectful arrows are not necessarily commutative, so the CCA transformations may be invalid. I did something very similar a couple years ago, by creating an arrow instance that generated TH expressions. IME the ghc optimizer handled it extremely well, and no extra optimizations were necessary. John L. On 14:43, Mon, Mar 2, 2015 Justin Bailey wrote:

Thomas,

I did some stuff with Hoopl a few years ago as part of my Master's thesis ("Using Dataflow Optimization Techniques with a Monadic Intermediate Language"). In Chapter 3 ("The Hoopl Library"), I wrote up an overview of Hoopl and work through a new example (new at the time, at least).

You can download my thesis from http://mil.codeslower.com. The example code from that chapter is available at https://github.com/m4dc4p/mil/blob/master/thesis/DeadCodeC.lhs. No guarantees that it still compiles, but I'm glad to try and help needed :)

...

Thomas

Hoopl works on control flow graphs, whereas Core is lambda calculus. I really don’t think Hoopl is going to be any good for optimising Core.

Ask the ghc-devs mailing list too. Someone there has been writing about arrows recently (take a look at the archive).

Simon

From: Thomas Bereknyei [mailto:tomberek@gmail.com] Sent: 02 March 2015 17:07 To: nr@cs.tufts.edu; Simon Peyton Jones Subject: Hoopl and Arrows

I've been interested in Arrows and their optimization recently. I've run into problems during basic tooling so I built a quasiquoter for proc notation (still working on rec and let statements, but the rest of it works) that converts from haskell-src-exts into a desugarred TH format. My original goal was to implement "Casual Commutative Arrows" [1] but to make it more user friendly and to include arrows with effects. I came across Hoopl and at first glance I would think it can help with Arrow optimization, especially with the tuple shuffling from desuggared proc-do notation. In spite of

On Mon, Mar 2, 2015 at 1:34 PM, Simon Peyton Jones wrote: the

...

slogan of "Hoopl: Dataflow Optimization made Simple" and the git repo's testing folder, I'm not 100% clear on Hoopl usage. I would be interested in anything that can get me started or even a thought or two whether it would be worth looking into for Arrows.

Simon, regarding [2], my quasiquoter can be rewritten to take `bind`, `bind_`, `fixA`, and `ifThenElseA` from scope rather than being built in. Would that help with #7828? I am not very familiar with GHC internals at the moment, and I am confused about the complexity of dsArrows.hs in contrast with my own parser. It seems I have a good start on it in the Parser module at [3], WARNING: untested and rough draft code, though suggestions and pointers are welcome. I was thinking of sending some of my code to haskell-src-meta because they can't yet translate their version of Exp into TH's ExpQ.

-Tom

[1] (https://hackage.haskell.org/package/CCA) [2] (https://ghc.haskell.org/trac/ghc/ticket/7828#comment:54) [3] (https://www.fpcomplete.com/user/tomberek/rulestesting)

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