Sorry if you've already explained this and I'm missing it, but for example,
suppose the current state on both sides is {:x {:y 1}}, and the 'sender'
wants to change to one of these states:
(a) {:x nil}
(b) {:x {}}
(b) {:x []}
(c) {:x {:y nil}}
Do you plan to support sending a different 'diff' in each of these cases,
such that the 'receiver' can end up in the same final state, for each of
these case?
Or perhaps the idea is that some of those are not supported?
Thanks,
Andy
On Fri, Feb 20, 2015 at 8:13 PM, Timothy Pratley <timothyprat...@gmail.com>
wrote:
> Hi Andy,
>
>
> On Fri, Feb 20, 2015 at 5:51 PM, Andy Fingerhut <andy.finger...@gmail.com>
> wrote:
>
>> The goal with your library is to transmit deltas between two systems, and
>> then apply those deltas to the other system to make them match, yes?
>>
>
> Correct, it works well for what I need it to do. :)
>
>
>> How would you use the diff return value ({:x {:y 1}} nil nil) to cause a
>> system that currently has {:x {:y 1}} to change to {:x {}}, as opposed to
>> some other state? That is, how would it know it needs to change the value
>> associated with :x to {} as opposed to removing the key :x and its value
>> entirely?
>>
>
> The short answer is (update-in state [:x] dissoc :y).
> Which is identical in result to (assoc state :x {}).
> So either representation could be used to accomplish the goal, and can be
> interchanged.
>
> As such I think either solution would be great! (and am happy to provide a
> patch either way).
>
>
> Below digresses from clojure.core/diff concerns, but I'm including it to
> more fully answer your question.
>
> I'll expand a little on the way patchin currently works. The second
> clojure.data/diff return value is used as replacements. The first item
> returned from clojure.data/diff is used as the keys to dissoc, excluding
> things that would be replaced anyway. If the patch size is greater than the
> target, just the target is sent. So in the end it constructs the same patch
> you described (as it is smaller). Valid patches look like either:
> [x]
> [diss replace]
> So the patch sent is
> [{:x {}}]
> Which means "replace the state with {:x {}}
> but for {:x {:y "foo", z "bar", w "baz"}} -> {:x {:z "bar", w "baz", q
> "bonza"}} the patch sent is
> [{:x {:y 1}} {:x {:q "bonza"}}]
> Which means "replace in state [:x :q] bonza, and strip out [:x :y].
> Plus some minor tricks to handle sets, and treat sequences as values.
> There are good resources for sequence diff compression but haven't thought
> of a good way to represent them in the same patch as a structural diff, and
> haven't had the need.
>
> I do not think clojure.data/diff need concern itself with optimization, as
> it currently serves the purpose of identifying differences very well, and
> optimization comes with calculation/size tradeoffs specific to the usage.
>
>
> Regards,
> Timothy
>
> --
> You received this message because you are subscribed to the Google
> Groups "Clojure" group.
> To post to this group, send email to clojure@googlegroups.com
> Note that posts from new members are moderated - please be patient with
> your first post.
> To unsubscribe from this group, send email to
> clojure+unsubscr...@googlegroups.com
> For more options, visit this group at
> http://groups.google.com/group/clojure?hl=en
> ---
> You received this message because you are subscribed to the Google Groups
> "Clojure" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to clojure+unsubscr...@googlegroups.com.
> For more options, visit https://groups.google.com/d/optout.
>
--
You received this message because you are subscribed to the Google
Groups "Clojure" group.
To post to this group, send email to clojure@googlegroups.com
Note that posts from new members are moderated - please be patient with your
first post.
To unsubscribe from this group, send email to
clojure+unsubscr...@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/clojure?hl=en
---
You received this message because you are subscribed to the Google Groups
"Clojure" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to clojure+unsubscr...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.
