Re: [ghc-steering-committee] #493: SPECIALISE with expressions, rec: accept

I'm supportive of this, if it doesn't break existing code (e.g. it supports existing code for at least a migration period, where it warns and gives concrete guidance on how to change the code). On Thu, 30 Nov 2023 at 20:15, Vladislav Zavialov wrote:

Great idea. I've worked on some code that uses SPECIALIZE pragmas with large type signatures, and it would become considerably more elegant if it could use type applications instead.

Vlad

On Wed, Nov 29, 2023 at 9:25 AM Adam Gundry wrote:

...

Dear all,

Richard and Simon propose to generalise SPECIALISE pragmas to allow expressions, not just type signatures:

https://github.com/ghc-proposals/ghc-proposals/pull/493

https://github.com/goldfirere/ghc-proposals/blob/specialise/proposals/0000-s...

This does not add anything fundamentally new, because such SPECIALISE pragmas can be translated using the existing RULES machinery, but it does make several idioms substantially more convenient:

* Using type applications in a SPECIALISE pragma to avoid repetition

* Manual call-pattern specialisation

* Loop unrolling

Thus I propose we accept this proposal.

Cheers,

Adam

-- Adam Gundry, Haskell Consultant Well-Typed LLP, https://www.well-typed.com/

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