[Freeciv-Dev] Re: [RFC] Path finding interface

[Raimar Falke <hawk@xxxxxxxxxxxxxxxxxxxxxxx>]

On Wed, Apr 10, 2002 at 05:23:35PM +0100, Gregory Berkolaiko wrote:
> On Wed, 10 Apr 2002, Raimar Falke wrote:
> 
> > On Wed, Apr 10, 2002 at 04:30:23PM +0100, Gregory Berkolaiko wrote:
> > > On Wed, 10 Apr 2002, Raimar Falke wrote:
> > 
> > > imagine: trireme is at point A, needs to go to B, the only path 
> > > A -> D2 -> D1 -> B (three moves, both Ds are dangerous).  You start with 
> > > only 2 moves.
> > 
> > Lets assume that the prototype is changed to
> >   bool (*wait_test)(int x, int y, int moves_left, void *user_data);
> > 
> > wait_test(a_x, a_y, 2, NULL) is called.
> > 
> > wait_test will look like
> > {
> >   square_iterate(x,y,moves_left,x1,y1) {
> >     if(is_shore(x1,y1)) return FALSE;
> >   }
> >   return TRUE;
> > }
> 
> doesn't work.
> we start at the shore therefore it will always return FALSE.
> 
> > But this will not always work. Since there is no guaranty that the
> > path this this one shore isn't blocked by any other means.
> 
> not just that, but you cannot tell if the shore you found in the 
> look-ahead is useful.
> 
> 
> > > One solution is to push the current point into the queue twice, with cost 
> > > 0 (corresponding to setting off at once) and with cost 2 (corresponding 
> > > to 
> > > waiting for 2 moves).
> > 
> > Possible but this will be expensive since it would double the elements
> > we have to consider. So it has to be selective.
> 
> 1. bool consider_waiting in the map structure to trigger it at all

In what map structure?

> 2. push only safe locations, obviously ;)

How will it recognize a safe location?

        Raimar

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