Re: [ghc-steering-committee] Wrapping up Constructor Synonyms and Pattern Synonym Signatures

That answers a question I had, thank you Simon. I'll do so. On Fri, Apr 28, 2017 at 2:46 AM, Simon Peyton Jones wrote:

| If there are no objections I will comment upon and close #41, comment | on #42, and then merge #42.

Yes -- but I'd like to see the author revise the text of #42 to incorporate feedback, so what we merge is the actual final proposal.

Simon

| -----Original Message----- | From: ghc-steering-committee [mailto:ghc-steering-committee- | bounces@haskell.org] On Behalf Of Christopher Allen | Sent: 28 April 2017 02:43 | To: Simon Marlow | Cc: ghc-steering-committee@haskell.org | Subject: Re: [ghc-steering-committee] Wrapping up Constructor Synonyms | and Pattern Synonym Signatures | | Your suggestions were most helpful anyone. Joachim, the wording you | chose especially helped, thank you! | | Here are my proposed replies to #41 and #42: | | #41: | | This proposal is rejected as it abandons the syntactic distinction | between constructors and the benefits described don't justify the | loss. | | | #42: This proposal is being accepted with some provisions. | | - The modifications should not change the behavior of existing pattern | synonyms that have not specified a type signature. | | - The proposal doesn't address the relationship between signatures of | the constructor and the signature of the pattern. The options | discussed in order of most conservative to least were: | * May not differ in anything but the constraints. | * Must have the same return type. | * Must have the same outer type constructor in their return type. | * No relation. | | The committee chose the first, most restricted, variant to follow the | principle of least surprise. If there's a strong belief that the | looser relationships may be useful, those can be described in a new | proposal. | | | If there are no objections I will comment upon and close #41, comment | on #42, and then merge #42. | | Thank you again everyone, | Chris | | | | | | On Thu, Apr 13, 2017 at 3:06 AM, Simon Marlow | wrote: | > Agree, I'm in favour of the conservative version of #42 and against | #41. | > | > But #42 also has a proposal for inference of the constructor type in | > the absence of a type signature, and gives several options there. I | > presume we want to be conservative and say that we're not making any | > changes to the behaviour in the absence of a type signature, right? | > | > Cheers | > Simon | > | > On 9 April 2017 at 21:16, Christopher Allen | wrote: | >> | >> Thank you to those of you that replied. I'd like to preserve the | >> syntactic distinction that construction synonyms eliminates. Your | >> statements have shifted me to a reject on | >> | https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgith | >> ub.com%2Fghc-proposals%2Fghc- | proposals%2Fpull%2F41&data=02%7C01%7Csim | >> | onpj%40microsoft.com%7C643cc13fb2564eee29f308d48dd7f244%7C72f988bf86f | >> | 141af91ab2d7cd011db47%7C1%7C0%7C636289406043033050&sdata=m090Oh7u4i3x | >> SXfTgj6uHqYnF4%2FnwBihOjhLfJy44dQ%3D&reserved=0 | >> | >> If no one has objections, I'd like to move to a reject as I think | >> enough time has elapsed that it's unlikely to get any defenders. | >> Speak up if you feel something was missed. | >> | >> | >> Regarding | >> | https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgith | >> ub.com%2Fghc-proposals%2Fghc- | proposals%2Fpull%2F42&data=02%7C01%7Csim | >> | onpj%40microsoft.com%7C643cc13fb2564eee29f308d48dd7f244%7C72f988bf86f | >> | 141af91ab2d7cd011db47%7C1%7C0%7C636289406043033050&sdata=rT%2FzUg328i | >> PKjA8dBKhZdVZObo1SQSJWlpmZtHTxm3E%3D&reserved=0 | >> | >> Summarizing peoples' replies so far: | >> | >> Joachim: In favor, as long as :i does the right thing. Seems | >> under-specified, suggested the following possible relationships | >> between signature of the pattern and the constructor: | >> | >> * May not differ in anything but the constraints. | >> * Must have the same return type. | >> * Must have the same outer type constructor in their return type. | >> * No relation. | >> | >> Roman: In favor of this proposal under the "May not differ in | >> anything but the constraints" policy and against it under any of | the | >> other three. | >> | >> Simon PJ: In favor of #42 alone, but no holes. Agrees with Roman | that | >> that type of the constructor should be the same as that of the | >> pattern. | >> | >> Simon Marlow: I believe the statement was in favor of #42 contra | #41, | >> but I didn't get a sense of how strongly or how Simon felt about | the | >> particulars. | >> | >> | >> I agree with and want to highlight Roman's point regarding, | >> | >> >A looser relationship between the constructor function and the | >> >pattern makes code significantly harder to read and the proposal | >> >doesn't include any justification for such a looser relationship | so | >> >I would go with the strongest requirement possible. | >> | >> | >> It seems to me like the respondents so far are in favor of #42, but | >> want the strongest variant. I'd like to move to accept #42 with the | >> "May not differ in anything but the constraints" variant. Any | >> objections? | >> | >> | >> Thank you Joachim for the status update last week. | >> | >> Thanks you for your time everyone, | >> Chris Allen | >> _______________________________________________ | >> ghc-steering-committee mailing list | >> ghc-steering-committee@haskell.org | >> https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering- | commit | >> tee | > | > | | | | -- | Chris Allen | Currently working on | https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fhaskel | lbook.com&data=02%7C01%7Csimonpj%40microsoft.com%7C643cc13fb2564eee29f | 308d48dd7f244%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C63628940604 | 3033050&sdata=5ExSGEwy6qgqGfi8HMtRjtkXVtObLQLBUN7xslCp%2BlU%3D&reserve | d=0 | _______________________________________________ | ghc-steering-committee mailing list | ghc-steering-committee@haskell.org | https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering- | committee

-- Chris Allen Currently working on http://haskellbook.com