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

[Raimar Falke <rf13@xxxxxxxxxxxxxxxxx>]

On Sun, Apr 13, 2003 at 04:51:46AM -0500, Jason Dorje Short wrote:
> Raimar Falke wrote:
> >On Sat, Apr 12, 2003 at 08:24:06AM +0200, Raimar Falke wrote:
> >
> >>>but square_iterate and other local functions cannot be implemented
> >>>in these coordinates
> >>
> >>Why not? In the worst case I calculate all the vectors by
> >>hand and hardcode them. Something like:
> >
> >
> >Actually there is a "portable" way to do square_iterate: using
> >MAPSTEP.
> >
> >At the start you go radius times NW.
> >
> >At the body you do a STEP W. This radius times. Than a STEP S. Than
> >radius steps E and so on.
> 
> This is a clever(ish) way to define an operation on "native" coordinates 
> that really uses map coordinates.  Unfortunately, in addition to 

> being extremely inelegant

I disagree. It is one place less which is topology dependent.

> it pushes the problem down the chain

Yes.

> how do you implement MAPSTEP?

Modifying DIR_D[XY]

> Additionally, you are defining map directions in terms of map
> coordinates, rather than native coordinates - even though you
> propose to remove map coordinates from the code.

In the current code everything is a map coordinate. Map coordinates in
your proposal are similar to the effective form in my proposal. My
coordinates however are similar to your native coordinates.

> If the directions don't even line up with your map, how is anyone
> supposed to understand what's going on?

I think it is easier to understand one set of coordinates where
MAPSTEP does a magic thing as multiple sets of coordinates.

> Finally, and as an additional challenge, how would you hack around the 
> problem for map_distance?

First solution: find it out by hand

Second solution: using your map coordinates ;) Basically do something
like:
 (dx,dy)=current_map_distance_vector(nat_to_map(input))
And then simplify the resulting expressions.

> Note, all of these are trivial if you are simply willing to do them
> in map coordinates.

Yes. But you don't have to scare people by introducing multiple
coordinates (you have scared and confused me) and if these are only
used in one function (map_distance_vector). square_iterate and MAPSTEP
can be easy done without them as outlines before.

        Raimar

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