_ already has the meaning of a type wildcard (generalized from its use as a wildcard in patterns), so this is consistent with its use in other type signatures. The problem I see with your proposal is that it assumes you know the names of the type variables in the original declaration.
On Tue, Aug 4, 2020 at 2:12 PM Anselm Schüler (conversations subemail) < conversat...@anselmschueler.com> wrote: > And also, it’s really weird and seems like a feature that should be > removed IMO. It kind of looks like the type variable _ is always > in-scope, and it’s unclear if the type of the resulting function is just > type variables without an explicit forall or if _ has a special meaning. > > > > *Anselm Schüler* > > *www.anselmschueler.com <http://www.anselmschueler.com>* > > > > *From: *Anselm Schüler (conversations subemail) > <conversat...@anselmschueler.com> > *Sent: *Tuesday, August 4, 2020 20:09 > *To: *Rowan Goemans <goemansro...@gmail.com>; ghc-devs@haskell.org > *Subject: *RE: AW: RE: Hi. I'm new to this mailing list and have a few > questions. > > > > True, but this makes the type less readable since id @_ :: _ -> _. > > > > *Anselm Schüler* > > *www.anselmschueler.com <http://www.anselmschueler.com>* > > > > *From: *Rowan Goemans <goemansro...@gmail.com> > *Sent: *Tuesday, August 4, 2020 19:59 > *To: *ghc-devs@haskell.org > *Subject: *Re: AW: RE: Hi. I'm new to this mailing list and have a few > questions. > > > > Just as a heads up. You can achieve what you want already by doing: > > f @_ @([String]) *:: forall a. (a, [String]) -> ([String], a**) * > > Best regards, > > Rowan Goemans > > On 8/4/20 7:45 PM, Anselm Schüler (conversations subemail) wrote: > > Thank you for the nice introduction :) ! > > I will check out the GHC proposals site. > > And following Simon’s (I hope addressing with first name is OK) > suggestion, I’m going to give an outline of the idea. > > > > The idea is to extend type application syntax to enable explicit > assignment of types to specific type variables. > > For instance, say I have f :: forall a b. (a, b) -> (b, a), and I want to > apply the type [String] to it. My only option is to do > > f @([String]) *:: forall b. ([String], b) -> (b, [String]) * > > —but what if, instead, I want a function of type forall a. (a, [String]) > -> ([String], a)? > > I propose the following syntax: > > f @{b = [String]} *:: forall a. ([String], b) -> (b, [String])* > > This wouldn’t break any existing programs since using record syntax here > is already disallowed and met with an error message. > > A question is of course the symbol used for assignment (~, =, ::, or ->?). > > > > I hope the code shows up as a monospace font on your end. I used the IBM > Plex Mono font, which is open-source <https://github.com/IBM/plex>. > > > > *Anselm Schüler* > > *wwwanselmschueler.com <http://www.anselmschueler.com>* > > *m...@anselmschueler.com <m...@anselmschueler.com>* > > > > *From: *Simon Peyton Jones <simo...@microsoft.com> > *Sent: *Tuesday, August 4, 2020 18:44 > *To: *Richard Eisenberg <r...@richarde.dev>; "Anselm Schüler > (conversations subemail)" <conversat...@anselmschueler.com> > *Cc: *ghc-devs@haskell.org > *Subject: *RE: Hi. I'm new to this mailing list and have a few questions. > > > > Welcome Anselm ghc-devs is a very informal mailing list, and we welcome > newcomers. > > > > For example, I have a feature idea in the back of my mind, which I imagine > would be easy to implement > > > > What Richard says is right, but you should feel free to fly the kite on > this list if you want – or on Haskell Café – to get some idea of whether > others seem warm about the idea, before writing a full proposal. > > > > Simon > > > > *From:* ghc-devs <ghc-devs-boun...@haskell.org> > <ghc-devs-boun...@haskell.org> *On Behalf Of *Richard Eisenberg > *Sent:* 04 August 2020 16:05 > *To:* "Anselm Schüler (conversations subemail)" > <conversation@anselmschuelercom> <conversat...@anselmschueler.com> > *Cc:* ghc-devs@haskell.org > *Subject:* Re: Hi. I'm new to this mailing list and have a few questions. > > > > Hi Anselm, > > > > Welcome! > > > > A good way of getting used to a list like this one is to wait a little > while and observe what kind of messages others send; this will give you a > feel for how the list is used. If you're impatient, you can also check out > the archives at https://mail.haskell.org/pipermail/ghc-devs/ > <https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fmail.haskell.org%2Fpipermail%2Fghc-devs%2F&data=02%7C01%7Csimonpj%40microsoft.com%7Ce68e6131af494519061c08d83887d962%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637321503404154244&sdata=w4QIMTGeMQ35bEo4xkOn2rIj8z02iMVje4Ar9AXM22k%3D&reserved=0> > . > > > > As for a feature request: if your feature changes the language GHC accepts > (most do), the right place to post is at > https://githubcom/ghc-proposals/ghc-proposals > <https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fghc-proposals%2Fghc-proposals&data=02%7C01%7Csimonpj%40microsoft.com%7Ce68e6131af494519061c08d83887d962%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637321503404164244&sdata=ogVVk5kRFXPc81dZ%2FiyGV9FbgQoQUtzazpFGcrAKUXA%3D&reserved=0>. > There is a description of how to proceed on that page. Proposals submitted > there get debated within the community and then eventually sent to a GHC > Steering Committee for a vote on acceptance or rejection. Then, we worry > about implementing it. If you have a suggestion that does not change the > language GHC accepts, you can post an Issue at > https://gitlab.haskell.org/ghc/ghc/ > <https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgitlab.haskell.org%2Fghc%2Fghc%2F&data=02%7C01%7Csimonpj%40microsoft.com%7Ce68e6131af494519061c08d83887d962%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637321503404164244&sdata=tg40q%2B9%2BW5KcVzHsPx9oCP7wdw5ipdZCOOdFnzUz3mU%3D&reserved=0> > . > > > > I hope this is helpful! > > Richard > > > > On Aug 4, 2020, at 8:59 AM, Anselm Schüler (conversations subemail) < > conversat...@anselmschueler.com> wrote: > > > > First of all, in general, I’m new to mailing lists (as used for > discussions) in general, so a question about that: > > When subscribed to the mailing list, do you get *every* message, or are > some discussions hidden? > > > > Second of all, I’d like to know what kinds of messages are appropriate > here. I’m not familiar with coding compilers or anything of the like, so > I’m somewhat afraid of offering unhelpful comments or being just woefully > underqualified to participate here. > > For example, I have a feature idea in the back of my mind, which I imagine > would be easy to implement (that might be wrong). Is it alright if I submit > that here or should I use some other forum? > > > > Thank you in advance for the answers. > > > > *Anselm Schüler* > > *www.anselmschueler.com > <https://nam06.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.anselmschueler.com%2F&data=02%7C01%7Csimonpj%40microsoft.com%7Ce68e6131af494519061c08d83887d962%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637321503404164244&sdata=WJBJ3P%2BFUnTmVs9Z97DHLat9mHr6vC22l0mQ36nafGc%3D&reserved=0>* > > *m...@anselmschueler.com <m...@anselmschueler.com>* > > _______________________________________________ > ghc-devs mailing list > ghc-devs@haskell.org > http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs > <https://nam06.safelinks.protection.outlook.com/?url=http%3A%2F%2Fmail.haskell.org%2Fcgi-bin%2Fmailman%2Flistinfo%2Fghc-devs&data=02%7C01%7Csimonpj%40microsoft.com%7Ce68e6131af494519061c08d83887d962%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637321503404174237&sdata=9y99aKPjfvm7WIH5Xv9JDlN7TIXdVPJZF%2BvAgbUvBUU%3D&reserved=0> > > > > > > > > _______________________________________________ > > ghc-devs mailing list > > ghc-devs@haskell.org > > http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs > > > > > _______________________________________________ > ghc-devs mailing list > ghc-devs@haskell.org > http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs > -- brandon s allbery kf8nh allber...@gmail.com
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