Interesting. There is a pretty high bar for changes to Core itself. Currently arrow notation desugars into Core with no changes. If you want to change Core, then arrow “notation” is actually much more than syntactic sugar. Go for it – but it would be a much more foundational change than previously, and hence would require more motivation.

From: Sophie Taylor [mailto:sophie@traumapony.org]
Sent: 22 October 2014 10:53
To: Simon Peyton Jones
Cc: ghc-devs@haskell.org
Subject: Re: Current description of Core?

Ah, thanks HEAPS. I've been banging my head against a wall for the last few days trying to see exactly what is going on :) I'm trying to find a way to minimise/eliminate the changes required to Core for the arrow notation rewrite - specifically, introducing kappa abstraction and application - semantically different to lambda abstraction/application but close enough that I can probably get away with either adding a simple flag to the Abstraction/Application constructors or doing it higher up in the HsExpr land, but the latter method leaves a sour taste in my mouth.

On 22 October 2014 19:35, Simon Peyton Jones <simonpj@microsoft.com> wrote:

Is the current description of Core still System FC_2 (described in https://www.seas.upenn.edu/~sweirich/papers/popl163af-weirich.pdf)?

We never implemented that particular version (too complicated!).

This is the full current story (thanks to Richard for keeping it up to date), in the GHC source tree

:

https://ghc.haskell.org/trac/ghc/browser/ghc/docs/core-spec/core-spec.pdf

Simon

From: ghc-devs [mailto:ghc-devs-bounces@haskell.org] On Behalf Of Sophie Taylor
Sent: 22 October 2014 10:26
To: ghc-devs@haskell.org
Subject: Current description of Core?

Hi,

Is the current description of Core still System FC_2 (described in https://www.seas.upenn.edu/~sweirich/papers/popl163af-weirich.pdf)?