[darcs-users] How to extend a patch theory to fully commute

James Cook jcook at cs.berkeley.edu
Sat Aug 8 20:51:28 UTC 2020


> > and whether it's okay to restrict S to be tree-like during the
> > intermediate steps. It is probably simpler to just drop the cycle
> > version and think only of trees, but I want to make sure I understand
> > how the primitive patch theory's commuting rules turn into tree
> > transformations.
>
> Why are you so hung up on this tree / cycle thing? What is wrong about
> your original context addresses and patch (sequence) adresses? If
> efficiency is the concern, we are talking about a factor of two here.
> This is irrelevant. For the theory you need to get the asymptotics
> right, the rest are implementation details.
>
> Cheers
> Ben

Sorry for the long silence; I was distracted by other things. I'm
hoping to take some time soon to review the thread and respond to
parts of it.

To respond to your quoted question above: I was concerned my
"canonical context address" representation of patches might not make
enough things equivalent, i.e. distinguish things that shouldn't be
distinguished.

This came up when we talked about inverses: we need to add some rule
in order to guarantee that the starting context of A^ equals the
ending context of A.

When I raised the concern, you suggested* "with inversion added, every
context address has two minimal forms: forward and backward, and these
denote the same extended context."

I was concerned that adding just that one new kind of equivalence
might not be enough. But I didn't think it through carefully. Honestly
I thought the cycle representation seemed kind of neat, but I guess I
don't really have a justification for it right now.

*https://lists.osuosl.org/pipermail/darcs-users/2020-July/027434.html

James


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