On 16 Jan 2017 04:43, "Lawrence Bottorff" <borgauf at gmail.com> wrote:
A while back I worked at an assessor's office, i.e., the people responsible for handling properties as land parcels. ...
... how property changed hands, and especially how
Hi Lawrence, I too worked on land parcels -- a local government rates billing and land valuation application. property lines
changed due to properties either merging or being split up. That is to say, how the parcel map changed over time.
I think the important aspect is that the a parcel can be split, and one of the splits merged with another parcel that was not originally with it. (I don't know how it was in your application. but in mine a legal parcel might consist of discontiguous areas of land -- for example a house in a terrace parcelled with a garage amongst a block of garages at the end of the street,) That is, looking over history you cannot group the parcels into a strict hierarchy of splits.
Somewhere in the functional paradigm, specifically recursion, would seem to be a model for this issue.
So in chapter 1 of any functional programming tutorial is
No I'm not seeing anything specifically functional about this. It's a directed graph, where each node is an instance of parcel ownership. the factorial
calculation function done with recursion. We beginners see the recursion "going out" to the "last one," then "coming back," adding up the results of each stage as it returns . . . like a yo-yo winding out, then winding up again.
Nice image, but there's no "last one" here (nor a "first one" that we could make sense of), There's no boundary from where we could be "coming back". Recursion does not apply [see more below]
David Turner dct25-561bs at mythic-beasts.com Mon Jan 16 07:47:41 UTC 2017
I suspect you have stumbled onto the dual concept of corecursion: ...
Nor corecursion. a) because of the infinite and arbitrary potential for splits/mergers; b) because even if there was some time in the distant past when the whole country was a single parcel with a single owner. (The Emperor? But even empires and countries split and merge. Or no owner, only hunter-gatherers/nomads, which might as well be a single parcel.) We're never going to try to rebuild that history. c) because there's never going to be a future end-state. Arbitrary splits/mergers will continue forever. We can't predict what might be the smallest parcels some area of land could be split into. (Note that one trick to prevent mineral exploitation companies from buying up glorious scenery is to split it into $1-parcels and sell each to a different owner.)
... Haskell being the most pure functional language, is, hence, my starting point on this question.
There's nothing specifically Haskell in this. A better place to ask might be lambda-the-ultimate. Anthony