[Freeciv-Dev] Re: [PATCH] Formatting cleanup.

[Gaute B Strokkenes <gs234@xxxxxxxxx>]

On Thu, 13 Sep 2001, jshort@xxxxxxxxxxxxx wrote:
> Gaute B Strokkenes wrote:
>>
>
>> b) the "you cannot necessarily attach a meaning to `normal', or
>> `normalized', or `wrapped', or whatever you prefer to call it, when
>> dealing with unreal coordinates" argument.  This is also incorrect,
>> as I have explained on a couple of occassions with no dissenters.
>
> I dissented then, and I dissent now.

Didn't you see my reply?  Silence is consent, you know.  That's
certainly how I interpreted things.

> There are some topologies that would not be particularly difficult
> to implement for which wrapping of non-real tiles has no good
> meaning whatsoever.
>
>        x x x
>      x x x x x
> <- x x x x x x x ->
> <- x x x x x x x ->
> <- x x x x x x x ->
>      x x x x x
>        x x x

I was referring to <87wv3lu4zr.fsf@xxxxxxxxx>.  I note that the
picture that you've drawn here is different from the one that you drew
last time, and that the picture you have drawn here represent
something that is more sensible than what you drew last time.

[ The difference was that the little arrows extended all the way to
  the top and bottom in the previous diagram.  This makes a BIG
  difference for the following argument.  ]

> Your only response was to make the incorrect claim that this is not
> a valid topology.

That is not what I said.  I said that you had constructed a topology
where the concept of normalization itself is not particularly valid
nor useful, whether applied to real or unreal tiles.

The reason was that there existed coordinate pairs wich could be
created either by starting at a real tile and making an "invalid" step
onto an unreal one, or by starting at another real tile and making a
"valid" step onto another real tile.  When confronted with such a
coordinate pair, normalize_map_pos() or is_real_tile() would not know
what value to return.  The technical reason for this is that your
topology could not be constructed as an equivalence class of Z x Z
under the action of vector displacements.  (Came to think of it,
neither could a Möbius strip, but the rules are broken in a way which
are much easier to work around in that case.)

> I also pointed out that any time you are wrapping an unreal
> coordinate you are doing something fundamentally, theoretically
> wrong.  I don't believe you responded to this at all.

Again, did you miss my reply entirely?  I think that the picture
difference may have impeded communication here, however.

   X   x x x           X   x x x
     x x x x x           x x x x x
<- x x x x x x x -> <- x x x x x x x ->
<- x x x x x x x -> <- x x x x x x x ->
<- x x x x x x x -> <- x x x x x x x ->
     x x x x x           x x x x x
       x x x               x x x

I do not see what you're talking about at all here.  In fact, this is
just a cylinder except that some tiles which are real on a cylinder
have now been declared unreal.  For instance, look at the unreal tile
marked with an upper-case X in the above picture.  Both of the X's are
the same tile.  They have the same real and unreal neighbours, and so
on.

There is another way to draw this topology, which probably makes this
clearer:

<- x x     X   x ->
<- x x x     x x ->
<- x x x x x x x ->
<- x x x x x x x ->
<- x x x x x x x ->
<- x x x     x x ->
<- x x         x ->

If you stil don't get it, try drawing your topology on the surface of
a cylinder.

--
Big Gaute                               http://www.srcf.ucam.org/~gs234/
Psychoanalysis??  I thought this was a nude rap session!!!