Hello,
On 4/13/06, Ross Paterson <[EMAIL PROTECTED]> wrote:
> They are equivalent, but C [a] b d, Num c and C [a] c d, Num c are not.
I agree that this is the case if you are thinking of
"forall a b c d. (C [a] b d, Num c) <=> (C [a] c d, Num c)"
Here is a counter example (assume we also add an i
On Thu, Apr 13, 2006 at 05:10:36PM -0700, Iavor Diatchki wrote:
> > > I understand the reduction steps. Are you saying that the problem is
> > > that the two sets are not syntactically equal? To me this does not
> > > seem important: we just end up with two different ways to say the same
> > > t
Hello,
> > I understand the reduction steps. Are you saying that the problem is
> > that the two sets are not syntactically equal? To me this does not
> > seem important: we just end up with two different ways to say the same
> > thing (i.e., they are logically equivalent).
>
> If c were mentio
On Thu, Apr 13, 2006 at 12:07:53PM -0700, Iavor Diatchki wrote:
> On 4/12/06, Claus Reinke <[EMAIL PROTECTED]> wrote:
> > that's why Ross chose a fresh variable in FD range position:
> > in the old translation, the class-based FD improvement rule no
> > longer applies after reduction because there'
Hello,
On 4/12/06, Claus Reinke <[EMAIL PROTECTED]> wrote:
> that's why Ross chose a fresh variable in FD range position:
> in the old translation, the class-based FD improvement rule no
> longer applies after reduction because there's only one C constraint
> left, and the instance-based FD improv
On Thu, 13 Apr 2006, Claus Reinke wrote:
(btw, in a real implementation, I wouldn't expect the memo constraints to
enter the constraint store at all - they are just a CHR-based way to express
a memo table, hence the name; as, in fact, I explained before even starting
that alternative translati
| there are interesting problems in FDs, but it seems that the
confluence
| problems were merely problems of the old translation, not anything
| inherent in FDs! I really had hoped we had put that phantom to rest.
Claus
You're doing a lot of work here, which is great. Why not write a paper?
Even
that's why Ross chose a fresh variable in FD range position:
in the old translation, the class-based FD improvement rule no
longer applies after reduction because there's only one C constraint
left, and the instance-based FD improvement rule will only instantiate
the 'b' or 'c' in the constrain
Hello,
I have been trying to follow this discussion, but I cannot quite
understand the problem.
On 4/10/06, Ross Paterson <[EMAIL PROTECTED]> wrote:
> One of the problems with the relaxed coverage condition implemented
> by GHC and Hugs is a loss of confluence. Here is a slightly cut-down
> versi
Do you have a revised set of restrictions on the form of instances?
sure, but you won't like them any better now than the last time I
mentioned them:-)
- as for confluence, none of the restrictions seem necessary
without FDs, type class inference proceeds by _matching_
of instance head
thanks, Tom!
indeed, for that old thread on an alternative translation, which forked from
an even older thread, I put aside all my wishlist and simply focussed on
removing what I considered anomalies in the operationalisation of type
classes with FDs via CHR in the old translation. the CHR re
On Mon, Apr 10, 2006 at 02:39:18PM +0100, Claus Reinke wrote:
class B a b | a -> b
class C a b c | a -> b
instance B a b => C [a] b Bool
Starting from a constraint set C [a] b Bool, C [a] c d, [...]
CHR-alt:
B a b <=> infer_B a b, memo_B a b.
memo_B a b1, memo_B a b2 ==>b1=b2.
C a b c <=> i
On Mon, Apr 10, 2006 at 02:39:18PM +0100, Claus Reinke wrote:
> >class B a b | a -> b
> >class C a b c | a -> b
> >
> >instance B a b => C [a] b Bool
> >
> >Starting from a constraint set C [a] b Bool, C [a] c d, [...]
>
> CHR-alt:
>
> B a b <=> infer_B a b, memo_B a b.
> memo_B a b1, memo_B a b2
On Mon, Apr 10, 2006 at 06:48:35PM +0100, Claus Reinke wrote:
> note also that we are talking about different things here: I am talking
> about FD consistency, you are talking about the FD consistency condition.
That would explain a few things.
> as this example shows once again, there are insta
On Mon, 2006-04-10 at 14:39 +0100, Claus Reinke wrote:
> > (see the FunctionalDependencies page for background omitted here)
>
> which seems to ignore much of the discussion of confluence we had
> here some weeks ago? I thought this list was for communication with
> the committee, and since the
On Mon, 10 Apr 2006, Claus Reinke wrote:
(see the FunctionalDependencies page for background omitted here)
which seems to ignore much of the discussion of confluence we had here some
weeks ago? I thought this list was for communication with the committee, and
since the ticket exists, I had b
there is no implication that d=Bool (you could add:
'instance B a b => C [a] b Char' without violating
FD consistency).
These instances (alpha-renamed):
instance B a1 b1 => C [a1] b1 Bool
instance B a2 b2 => C [a2] b2 Char
violate the consistency condition: a substitution that unifies a1 and
a
om: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of
| Ross Paterson
| Sent: 10 April 2006 09:53
| To: haskell-prime@haskell.org
| Subject: FDs and confluence
|
| (see the FunctionalDependencies page for background omitted here)
|
| One of the problems with the relaxed coverage condition impl
On Mon, Apr 10, 2006 at 02:39:18PM +0100, Claus Reinke wrote:
> >instance B a b => C [a] b Bool
> >
> >Starting from a constraint set C [a] b Bool, C [a] c d,
>
> there is no implication that d=Bool
> (you could add: 'instance B a b => C [a] b Char' without violating
> FD consistency).
These inst
(see the FunctionalDependencies page for background omitted here)
which seems to ignore much of the discussion of confluence we had
here some weeks ago? I thought this list was for communication with
the committee, and since the ticket exists, I had been hoping that the
type class subcommitte
On Mon, Apr 10, 2006 at 05:49:15PM +0800, Martin Sulzmann wrote:
> Ross Paterson writes:
> > 1) consider the two constraint sets equivalent, since they describe
> >the same set of ground instances, or
>
> That's troublesome for (complete) type inference.
> Two constraint stores are equivalen
Ross Paterson writes:
> (see the FunctionalDependencies page for background omitted here)
>
> One of the problems with the relaxed coverage condition implemented
> by GHC and Hugs is a loss of confluence. Here is a slightly cut-down
> version of Ex. 18 from the FD-CHR paper:
>
> clas
(see the FunctionalDependencies page for background omitted here)
One of the problems with the relaxed coverage condition implemented
by GHC and Hugs is a loss of confluence. Here is a slightly cut-down
version of Ex. 18 from the FD-CHR paper:
class B a b | a -> b
class C a b c |
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