[Freeciv-Dev] Re: (PR#3936) introducing native coordinates

[Jason Dorje Short <vze49r5w@xxxxxxxxxxx>]

Raimar Falke wrote:
> On Wed, Apr 09, 2003 at 06:30:12AM -0500, Jason Dorje Short wrote:
>
> > > That is quite possible. I'm still trying to understand.
>
> Another try. See the two attached pictures. So there is a compact form
> and a rotated form. Both are identical for non-iso maps. In addition
> there is the view form which it hard to draw so I use ascii here.
I think you're just getting more confused - and certainly you are 
confusing me.
Try using the same nomenclature that we are using.  There are three 
forms - the map form, the natural form, and the native form. 
Additionally there is the iso-view form and the non-iso view form (which 
may correspond to one of the above forms, but only by lucky 
coincidence).  You may want to read back over the original patch.
> View form (iso tileset):
>
>     a b c d e f g h i
> 1   # # # # # # # # #       Since it isn't clear I specify that the
> 2    # # # # # # # # #      tile right below b1 is called b2 and not a2.
> 3   # # # # # # # # #
> 4    # # # # # # # # #
> 5   # # # # # # # # #
This is the iso-view form.  It also happens to be the natural form for 
an iso map.
> View form (non-iso tileset):
>   Similar to grid_rot.png.
>
> The view form is irrelevant for the semantics of the functions since
> it depends on the view (iso tileset or non-iso one)?! It looks like
> this is untrue: you specify the semantics of the function based on the
> iso tileset view form since otherwise the semantic of
> square_map_iterate doesn't changes (it is the same for compact and
> rotated form). Yes/no?
I don't know what this means.

> So square_map_iterate(d3) is
>
>     a b c d e f g h i
> 1   # # # o # # # # #
> 2    # # o o # # # # #
> 3   # # o + o # # # #
> 4    # # o o # # # # #
> 5   # # # o # # # # #
Yes.  But it is easier to think of it in map coordinates:
   21 a
  43 # b
  5 ### c
   ##### d
    ##ooo e
     #ooo# f
      ooo## g
       ##### i
        #####
         ####
          ##

which means that, in map coordinates, the semantics are unchanged from 
the original.
> which is in the compact form
>
>     a b c d e f g h i
> 1   # # # o # # # # #
> 2   # # o o # # # # #
> 3   # # o + o # # # #
> 4   # # o o # # # # #
> 5   # # # o # # # # #
>
> That is [c2, c3, c4, d1, d2, d4, d5, e3]. Yes/no?
In native coordinates, yes.  That's why we don't use native coordinates 
for local operations :-).
> Just for completeness: if we define this semantics of the operations
> at the compact or the rotated for the answer would be:
>
> square_map_iterate(d3)
>     a b c d e f g h i
> 1   # # # # # # # # #
> 2   # # o o o # # # #
> 3   # # o + o # # # #
> 4   # # o o o # # # #
> 5   # # # # # # # # #
>
> That is [c2, c3, c4, d2, d4, e2, e3, e4].
If you define square_nat_iterate, i.e., define the semantics in terms of 
native coordinates this is what you would get.  Note that this block 
would be quite useless, it would give you a shape like
     o
    ooo         o o o
   o+o    <=>  o + o
   oo           o o o

which would have a different shape than square_nat_iterate(d2):

                 oo
  o o o         o+o
   o + o  <=>  ooo
  o o o         o

> I'm hoping that we get slowly get to the core of the things.
Try to work with the existing terms rather than defining entirely new 
ones.  The concept of "compact" and "rotated" may vary depending on the 
topology, and is not complete.  "natural", "native", and "map", on the 
other hand, were pretty thoroughly defined.
jason