Is it time to start deprecating FunDeps?
Martin Sulzmann
martin.sulzmann at gmail.com
Wed May 1 13:08:58 CEST 2013
Comments see below.
On Wed, May 1, 2013 at 11:13 AM, AntC <anthony_clayden at clear.net.nz> wrote:
>> Martin Sulzmann <martin.sulzmann at ...> 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 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 z1, Sum x y z2 ==> z1 ~ z2
enforced by
Sum x y z | x y -> z
In my TF encoding, we find a similar derivation step
SumF1 x y ~ z1, SumF1 x y ~ z2 ==> z1 ~ z2
So, you're asking can we translate/express FDs using GHC intermediate language
with plain type equations only?
-Martin
> And that's exactly
> because I want to use overlapping.
>
> (You've also failed to understand that the Sum example is for doing Peano
> Arith. See the solution I've just posted.)
>
>
>
>
>
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