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
Interesting! It'd be great if you've found a simpler more uniform rule.
(Which you seem to be getting rather good at.)Let's see if you can
convince Martin, first, and then articulate the proposed rules. I'll
look fwd to that.
Simon
| -Original Message-
| From: [EMAIL PROTECTED]
[mai
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
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