Re: [Haskell-cafe] The Definition of Haskell

Thanks, all, this was indeed what I was looking for, with the reference to Ott as an added bonus. It looks like formalizing and proving safety for this system in a proof assistant would make a good project. --Todd On Mon, Dec 18, 2017 at 1:42 AM Simon Peyton Jones wrote:

I see SPJ's point, but he makes another point in the same video, which is that Haskell has a small, internal core language to which everything must elaborate, so this would seem to make formalization even more attractive: formalize and prove safety for the core language once and for all, and then specify the elaborations and check their properties modularly, which should work well even in the face of language evolution.

Yes – and Core is indeed formalised quite carefully (by Richard Eisenberg). See https://ghc.haskell.org/trac/ghc/ticket/14572#comment:8

Simon

*From:* Haskell-Cafe [mailto:haskell-cafe-bounces@haskell.org] *On Behalf Of *Todd Wilson *Sent:* 17 December 2017 19:53 *To:* Haskell Cafe *Subject:* Re: [Haskell-cafe] The Definition of Haskell

On Sat, Dec 16, 2017 at 9:14 PM Brandon Allbery wrote:

Dunno about safety results, but https://www.haskell.org/onlinereport/haskell2010/ exists (next revision expected in 2020 iirc).

Although this can be considered a definition of the language, it is by no means a formal definition of the static and dynamic semantics of the language in a form amenable to representation in systems like Coq, where metatheory might be checked.

On Sat, Dec 16, 2017 at 9:22 PM Baojun Wang wrote:

SPJ may answered part of it in his talk Escape from the ivory tower: https://www.youtube.com/watch?v=re96UgMk6GQ&feature=share https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3Dre96UgMk6GQ%26feature%3Dshare&data=02%7C01%7Csimonpj%40microsoft.com%7C6fb497b3f6c94c81876e08d545882101%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636491373335007410&sdata=5WnVwESDGAotRmeUq6wevSmwgsg6hFFGe6c90YYFv6E%3D&reserved=0 from about 29 minutes.

Nice talk; thanks for the reference. To summarize: formalization, which is a lot of work, leads to standardization and the reluctance to change the language, and one of Haskell's strong points is that it is constantly evolving.

I see SPJ's point, but he makes another point in the same video, which is that Haskell has a small, internal core language to which everything must elaborate, so this would seem to make formalization even more attractive: formalize and prove safety for the core language once and for all, and then specify the elaborations and check their properties modularly, which should work well even in the face of language evolution.