[Freeciv-Dev] Re: Map coordinate cleanups.

[David Pfitzner <dwpfitzner@xxxxxxxxx>]

Gaute B Strokkenes <gs234@xxxxxxxxx> wrote:

> You have basically understood everything.  The only thing that I have
> to add is this: normalization is independent of realness.

I'm not so sure (see below), and even if this is so, I have to agree 
with Trent that it seems like a distinction which is not useful in 
practice.

> Consider for instance, the coordinates (2, 0).  That's a real tile,
> and the coordinates are normalized.  If we go north, we arrive at
> (2, -1).  That's not a real tile.
> 
> Now supposed that we started with (2+xsize, 0) instead.  That's the
> same tile, but this time the coordinates are not normalized.  Now we
> go north again, and arrive at (2+xsize, -1).

Thats not a real tile either.  Since neither (2, -1) nor (2+xsize,-1)
is real, you cannot do anything with either, so why do you care if
they don't look the same?  I don't consider this a paradox. 

Also, arguably you should not in practice "go north" from a 
non-normalized set of coordinates: normalize them first, then do 
further processing/offsetting.

> If we accept that normalisation does not apply to non-real tile
> coordinates, then we have to accept that if we start with equivalent
> tile coordinates and perform the same steps then we will end up at
> different tiles.  To me, that's highly counterintuitive.

They are not different tiles, since neither is a (real) tile.

Regarding whether non-real tiles can be normalized or not,
what if you had a normalization where the x-wrapping depending
on the y-coordinate?  Then if y is out of range, it may be
ill-defined (or arbitrarily defined) whether x is normalized
or not.  (Admittedly such a scheme may run into other problems.)

-- David

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