Ultimately this is the wrong forum for this discussion as neither type
equalities nor functional dependencies are in Haskell' at this time.
On Wed, May 1, 2013 at 7:04 PM, AntC wrote:
> > Martin Sulzmann writes:
>
> > > On Wed, May 1, 2013 at 11:13 AM, AntC wrote:
> > >
> > > I want to replac
> Martin Sulzmann writes:
> > On Wed, May 1, 2013 at 11:13 AM, AntC wrote:
> >
> > I want to replace FD's with Equality Constraints.
>
> Ok, that's the bit I've missed, but then I argue that you can't fully
> encode FDs.
>
> Consider again the 'Sum' example.
>
> In the FD world:
>
> Sum x y
That would be cool!
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Er, what I meant was
class Foo s t a b | s -> a, t -> b, s b -> t, t a -> s
That is what I get for dashing it off off the cuff. =)
Then s determines some type argument for it, t determines its type
argument, but Using s and the other type argument I can determine the whole
containing type 't' an
Dear Haskellers,
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formed, and we would be delighted to receive your proposals for changes
to the language. Please see
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Comments see below.
On Wed, May 1, 2013 at 11:13 AM, AntC wrote:
>> Martin Sulzmann writes:
>>
>> (1) There's a mechanical way to translate FD programs with
>> non-overlapping instances to TF (and of course vice versa).
>
> Martin, no! no! no! You have completely mis-understood.
>
> I do _not_ _
On Tue, Apr 30, 2013 at 11:35:10PM -0400, Edward Kmett wrote:
>
> I have dozens of classes of forms like
>
> class Wrapped s t a b | a -> s, b -> t, a t -> s, b s -> t
Isn't this equivalent to just
class Wrapped s t a b | a -> s, b -> t
?
Thanks
Ian
> Martin Sulzmann writes:
>
> (1) There's a mechanical way to translate FD programs with
> non-overlapping instances to TF (and of course vice versa).
Martin, no! no! no! You have completely mis-understood.
I do _not_ _not_ _not_ want to replace FD's with TF's.
I want to replace FD's with Equa
> AntC writes:
>
> > ...> writes:
> >
> > I think this mechanical way is not complete.
>
On further thought/experiment, I rather think it is -- for one of your
counter examples.
Firstly, I apologise to Oleg. I had mis-remembered his solution to the
class Sum example ...
>
> >
> >
(1) There's a mechanical way to translate FD programs with
non-overlapping instances to TF (and of course vice versa). For
example, let's reconsider Oleg's example.
> {-# LANGUAGE MultiParamTypeClasses, FunctionalDependencies #-}
> {-# LANGUAGE TypeFamilies #-}
> {-# LANGUAGE FlexibleContexts #-}
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