[Freeciv-Dev] Re: example patch: [xy]_map_iterate

[Raimar Falke <hawk@xxxxxxxxxxxxxxxxxxxxxxx>]

On Thu, Oct 04, 2001 at 07:58:22AM -0400, Jason Dorje Short wrote:
> Raimar Falke wrote:
> > 
> > On Thu, Oct 04, 2001 at 07:00:01AM -0400, Jason Dorje Short wrote:
> > > Raimar Falke wrote:
> > > >
> > > > On Thu, Oct 04, 2001 at 05:57:09AM -0400, Jason Dorje Short wrote:
> > > > > There's a lot of code that can't use whole_map_iterate because the
> > > > > iteration has to happen in a certain order.
> > > >
> > > > What code? I don't have a good feeling with code that has such
> > > > dependencies. Printing the map?
> > >
> > > Printing the map (to some random text file, I presume) is part of it.
> > > Also saving the game and sending tiles across the network.  These depend
> > > strictly upon the ordering, so are easy to fix using [xy]_map_iterate.
> > 
> > So what code would be used (after preprocessor expansion) instead of
> > 
> >   for(y=0; y<map.ysize; y++) {
> >     char *terline=secfile_lookup_str(file, "map.l%03d", y);
> > 
> >     for(x=0; x<map.xsize; x++) {
> >       char ch=terline[x];
> > 
> > with an isometric map? Will there be map.xsize and map.ysize in an
> > isometric map?
> 
> There may be map.xsize and map.ysize; this depends on the
> implementation.  You could also do a single array using map_pos_to_index
> and the inverse.  In any case though there will be some single value
> that represents the maximum X and Y width; call them map_[xy]_size().
> 
>   for(y=0; y<map_y_size(); y++) {
>     char *terline=...
> 
>     for(y=0; y<map_x_size(); x++) {
>       char ch=terline[x];
>       if(!is_normal_map_pos(x, y)) continue;
>       ...
> 
> But, some special handling may be necessary in the case of off-the-map
> coordinate positions.  Everything will have to be fixed up case-by-case.
> 
> > > Other examples don't iterate over the whole map...for instance some
> > > iterate over just the poles while others skip border positions.  These
> > > can be done with whole_map_iterate by skipping invalid positions; the
> > > problem here is that the current definition of "valid" is
> > > topology-dependent (it assumes the current wrapping system).  These will
> > > take a little time to figure out.
> > 
> > For the poles I can imagine a rectangle_iterare.
> 
> No...the problem is "polar" may vary from topology to topology.  In an
> isometric map polar regions will run diagonally along two sides, so a
> rectangular iteration will not work.  In the more general case, it may
> be desirable to have polar regions defined by the ruleset or server
> options - in a taurus topology, what regions are polar?  Or, perhaps the
> ruleset should just define "north" and "south" and let the game figure
> it out (this would fail for a topology that was not well-oriented).
> 
> static void make_fair(void)
> {
>   whole_map_iterate(x, y) {
>     if (!IS_POLAR(x, y)) {
>       ...
>     }
>   } whole_map_iterate_end;
> 
> Add to this complication: in make_fair() I'm not sure if the correct
> restriction is IS_POLAR (which is true of the northernmost and
> southernmost 2 tiles) or IS_NEAR_BORDER (also true of the northernmost
> and southernmost 2 tiles).  Ross's patch has a cleverly incomprehensible
> algorithm for this that wouldn't work under isometric topologies - I
> can't tell from it one way or the other.

Now I have another basic question:

   a
  bcd
 efghi
  jkl
   m

For which tiles is y==0? a OR e,b and a? Or isn't this an isometric
map? And the following is:?

        / North
   n  /
  o p 
 q r s
  t u
   v

The same map rotated (non-isometric now):

 n p s
 o r u
 q t v

The adjacent property is the same.

       /
-     # \4
|    # # \
|   # # #  \/
6    # # # 
|     # # \
-      # / 3
        \

    |--6-|

The game has to know somewhere the this map above is 3x4.

The more I think about this the more I think that the easiest way is
to leave the current system in place and introduce a new name/position
space. Normal positions are called map positions and the new ones are
called user positons. If there is a non-isometric map there would a
1:1 mapping of map pos to user pos and back. If there is a isometric
map is used the mapping would be more complicated. Neighbor properties
and distances are only defined on user positions.

Summary: before I don't understand this issue and especially the end
result fully there will be no changes by me. What
coordinates/positions are there? What semantic they represent (where
is north and south)?

        Raimar

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 email: rf13@xxxxxxxxxxxxxxxxx
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