[Freeciv-Dev] Re: (PR#6285) rand_map_pos using native coordinates

["Jason Short" <jdorje@xxxxxxxxxxxxxxxxxxxxx>]

Jason Short wrote:
> This simple patch rewrites rand_map_pos to use native coordinates.  This 
> allows it to work with iso-maps.

> +  native_to_map_pos(x, y, myrand(map.xsize), myrand(map.ysize));

Except, with a macro form of native_to_map_pos, that will not work.  At 
all.  This new patch is better.


FYI, in gen-topologies (which is pretty well tested) the function looks like

+  int nat_x, nat_y;
+
+  nat_x = myrand(map.xsize);
+  nat_y = myrand(map.ysize);
+  native_to_map_pos(x, y, nat_x, nat_y);
+  assert(is_normal_map_pos(*x, *y));

which is close to the attached version.  Just a matter of taste, I suppose.

jason

Index: common/map.c
===================================================================
RCS file: /home/freeciv/CVS/freeciv/common/map.c,v
retrieving revision 1.145
diff -u -r1.145 map.c
--- common/map.c        2003/09/25 20:55:01     1.145
+++ common/map.c        2003/09/25 21:10:09
@@ -1489,10 +1489,11 @@
 **************************************************************************/
 void rand_map_pos(int *x, int *y)
 {
-  do {
-    *x = myrand(map.xsize);
-    *y = myrand(map.ysize);
-  } while (!is_normal_map_pos(*x, *y));
+  int nat_x = myrand(map.xsize), nat_y = myrand(map.ysize);
+
+  /* Don't pass non-deterministic expressions to native_to_map_pos! */
+  native_to_map_pos(x, y, nat_x, nat_y);
+  CHECK_MAP_POS(*x, *y);
 }
 
 /**************************************************************************