RE: status of rebindable syntax for arrows
| It already has a bug entry: #7828. What would help is to know the
| kind of use you have in mind, to see whether it fits with the proposed
| solution.
Indeed. Moreover #7828 is stalled; it needs some arrow-savvy person to focus
cycles on it. If rebindable syntax for arrows is considered important.
Meanwhile I think you should not rely on rebindable syntax for arrows. The user
manual is misleading on this point.
Simon
| -Original Message-
| From: Glasgow-haskell-users [mailto:glasgow-haskell-users-
| boun...@haskell.org] On Behalf Of Ross Paterson
| Sent: 15 October 2014 06:56
| To: glasgow-haskell-users
| Subject: Re: status of rebindable syntax for arrows
|
| On Tue, Oct 14, 2014 at 10:26:46PM +0200, S. Doaitse Swierstra wrote:
| > The GHC manual already for quite a number of version states:
| >
| >• Arrow notation (see Section 7.17, “Arrow notation ”) uses
| whatever arr, (>>>), first, app, (|||) and loop functions are in
| scope.
| > But unlike the other constructs, the types of these
| functions must match the Prelude types very closely. Details are in
| flux; if you want to use this, ask!
| >
| > When using this feature we get the error:
| >
| > "Var/Type length mismatch:
| >[s{tv aVL} [tv]]
| >[]
| > ghc: panic! (the 'impossible' happened) (GHC version 7.8.3 for
| > x86_64-apple-darwin):
| >tcTyVarDetails s{tv aVL} [tv]
| >
| > Please report this as a GHC bug:
| http://www.haskell.org/ghc/reportabug";
| >
| > So our question is whether we should really report this as a bug,
| and/or what we can do about this.
|
| It already has a bug entry: #7828. What would help is to know the
| kind of use you have in mind, to see whether it fits with the proposed
| solution.
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Re: status of rebindable syntax for arrows
On Tue, Oct 14, 2014 at 10:26:46PM +0200, S. Doaitse Swierstra wrote:
> The GHC manual already for quite a number of version states:
>
> • Arrow notation (see Section 7.17, “Arrow notation ”) uses whatever
> arr, (>>>), first, app, (|||) and loop functions are in scope.
> But unlike the other constructs, the types of these functions must
> match the Prelude types very closely. Details are in flux; if you want to use
> this, ask!
>
> When using this feature we get the error:
>
> "Var/Type length mismatch:
>[s{tv aVL} [tv]]
>[]
> ghc: panic! (the 'impossible' happened)
> (GHC version 7.8.3 for x86_64-apple-darwin):
> tcTyVarDetails s{tv aVL} [tv]
>
> Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug";
>
> So our question is whether we should really report this as a bug, and/or what
> we can do about this.
It already has a bug entry: #7828. What would help is to know the kind
of use you have in mind, to see whether it fits with the proposed solution.
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status of rebindable syntax for arrows
The GHC manual already for quite a number of version states:
• Arrow notation (see Section 7.17, “Arrow notation ”) uses whatever
arr, (>>>), first, app, (|||) and loop functions are in scope.
But unlike the other constructs, the types of these functions must
match the Prelude types very closely. Details are in flux; if you want to use
this, ask!
When using this feature we get the error:
"Var/Type length mismatch:
[s{tv aVL} [tv]]
[]
ghc: panic! (the 'impossible' happened)
(GHC version 7.8.3 for x86_64-apple-darwin):
tcTyVarDetails s{tv aVL} [tv]
Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug";
So our question is whether we should really report this as a bug, and/or what
we can do about this.
Thanks for your help,
Doaitse
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