...@haskell.org; Simon Peyton-Jones; GHC
Users Mailing List
Subject: Re: Fundeps and type equality
Yes, I finished and pushed in December. A description of the design and how to
use the feature is here:
http://hackage.haskell.org/trac/ghc/wiki/NewAxioms
There's also a section (7.7.2.2 to be exact
; Simon Peyton-Jones;
GHC Users Mailing List
Subject: Re: Fundeps and type equality
Yes, I finished and pushed in December. A description of the design and how
to use the feature is here:
http://hackage.haskell.org/trac/ghc/wiki/NewAxioms
There's also a section (7.7.2.2 to be exact
| The -XOverlappingInstances flag instructs GHC to allow more than one
| instance to match, provided there is a most specific one. For example,
| the constraint C Int [Int] matches instances (A), (C) and (D), but the
| last is more specific, and hence is chosen. If there is no most-specific
|
Of *Iavor Diatchki
*Sent:* 26 December 2012 02:48
*To:* Conal Elliott
*Cc:* glasgow-haskell-b...@haskell.org; GHC Users Mailing List
*Subject:* Re: Fundeps and type equality
** **
Hello Conal,
** **
GHC implementation of functional dependencies is incomplete: it will use
functional
2012 02:48
To: Conal Elliott
Cc: glasgow-haskell-b...@haskell.org; GHC Users Mailing List
Subject: Re: Fundeps and type equality
Hello Conal,
GHC implementation of functional dependencies is incomplete: it will use
functional dependencies during type inference (i.e., to determine
On January 11, 2013 13:55:58 Simon Peyton-Jones wrote:
| The -XOverlappingInstances flag instructs GHC to allow more than one
| instance to match, provided there is a most specific one. For example,
| the constraint C Int [Int] matches instances (A), (C) and (D), but the
| last is more
*To:* Conal Elliott
*Cc:* glasgow-haskell-b...@haskell.org; GHC Users Mailing List
*Subject:* Re: Fundeps and type equality
** **
Hello Conal,
** **
GHC implementation of functional dependencies is incomplete: it will
use functional dependencies during type inference (i.e
: 26 December 2012 02:48
To: Conal Elliott
Cc: glasgow-haskell-b...@haskell.org; GHC Users Mailing List
Subject: Re: Fundeps and type equality
Hello Conal,
GHC implementation of functional dependencies is incomplete: it will use
functional dependencies during type inference (i.e
:* glasgow-haskell-b...@haskell.org; GHC Users Mailing List
*Subject:* Re: Fundeps and type equality
** **
Hello Conal,
** **
GHC implementation of functional dependencies is incomplete: it will use
functional dependencies during type inference (i.e., to determine the
values of free type
On January 10, 2013 13:56:02 Richard Eisenberg wrote:
Class instances that overlap are chosen among by order of specificity;
Sorry to jump in the middle here, but this caught my attention as this sort of
specificity determination is exactly what I had in mind when I was working on
my The shape
-haskell-users@haskell.org
| Cc: Richard Eisenberg; Martin Sulzmann; Simon Peyton-Jones
| Subject: Class instance specificity order (was Re: Fundeps and type equality)
|
| On January 10, 2013 13:56:02 Richard Eisenberg wrote:
| Class instances that overlap are chosen among by order of specificity
On Thu, 2013-01-10 at 22:17 +, Simon Peyton-Jones wrote:
Is
http://www.haskell.org/ghc/docs/latest/html/users_guide/type-class-extensions.html#instance-overlap
insufficiently clear? If so, let's clarify it.
Thanks for getting back to me Simon. The document says
For example, consider
December 2012 02:48
To: Conal Elliott
Cc: glasgow-haskell-b...@haskell.org; GHC Users Mailing List
Subject: Re: Fundeps and type equality
Hello Conal,
GHC implementation of functional dependencies is incomplete: it will use
functional dependencies during type inference (i.e
...@haskell.org] *On Behalf Of *Iavor Diatchki
*Sent:* 26 December 2012 02:48
*To:* Conal Elliott
*Cc:* glasgow-haskell-b...@haskell.org; GHC Users Mailing List
*Subject:* Re: Fundeps and type equality
** **
Hello Conal,
** **
GHC implementation of functional dependencies
: 26 December 2012 02:48
To: Conal Elliott
Cc: glasgow-haskell-b...@haskell.org; GHC Users Mailing List
Subject: Re: Fundeps and type equality
Hello Conal,
GHC implementation of functional dependencies is incomplete: it will use
functional dependencies during type inference (i.e., to determine
-haskell-bugs-boun...@haskell.org] *On Behalf Of *Iavor Diatchki
*Sent:* 26 December 2012 02:48
*To:* Conal Elliott
*Cc:* glasgow-haskell-b...@haskell.org; GHC Users Mailing List
*Subject:* Re: Fundeps and type equality
** **
Hello Conal,
** **
GHC implementation of functional
Hi Iavor,
Thanks much for the explanation.
Before this experiment with FDs, I was using a type family. I tried
switching to FDs, because I wanted the compiler to know that the family is
injective in order to assist type-checking. Can we declare type families to
be injective? Now I see that I ran
I presume that injectivity of type families is the sole reason why data
families exist.
Roman
* Conal Elliott co...@conal.net [2012-12-26 10:23:46-0800]
Hi Iavor,
Thanks much for the explanation.
Before this experiment with FDs, I was using a type family. I tried
switching to FDs,
I don't think that's true (though a few minutes of searching has not
yet turned up anything describing the original motivation for data
families). Sometimes you really do want to construct a family of new
data types, instead of just mapping to existing ones. I think
everyone agrees that using
* Brent Yorgey byor...@seas.upenn.edu [2012-12-26 14:49:16-0500]
I don't think that's true (though a few minutes of searching has not
yet turned up anything describing the original motivation for data
families). Sometimes you really do want to construct a family of new
data types, instead of
Hello Conal,
GHC implementation of functional dependencies is incomplete: it will use
functional dependencies during type inference (i.e., to determine the
values of free type variables), but it will not use them in proofs, which
is what is needed in examples like the one you posted. The reason
21 matches
Mail list logo
