[Freeciv-Dev] Re: PATCH: rand_pos function and usage (PR#1017)

[Raimar Falke <hawk@xxxxxxxxxxxxxxxxxxxxxxx>]

On Tue, Oct 23, 2001 at 09:32:54AM -0700, jdorje@xxxxxxxxxxxxxxxxxxxxx wrote:
> Raimar Falke wrote:
> > 
> 
> <snip snip snip>
> 
> > It looks like the filter approach and the "classical" approach both
> > have cases were one is faster. What do you think about a general
> > interface:
> > 
> > #define RAND_POS(x, y, pos_check,max_count)
> >    if(max_count==0)
> >       RAND_POS_CHECKED(x,y,pos_check);
> >    else
> >    {
> >     do {
> >       x=myrand(map.xsize);
> >       y=myrand(map.ysize);
> >     } while (!(pos_check(x,y)) && max_count-->0);
> >    }
> > 
> > Now the programmer can choose based on number he collected which
> > approach he uses.
> 
> What about something like this?

Is it needed to have multiple map positions?

> +/* Determines whether the position is normal given that it's in
> +   the range 0<=x<map.xsize and 0<=y<map.ysize.  It's primarily a
> +   faster version of is_normal_map_pos since such checks are pretty
> +   common. */

> +#define is_normal_map_pos2(x, y) (1)

IMHO this name is still not acceptable.

> +/* Parameters:
> + *   x_arr, y_arr: arrays (or single pointers) for the x and y coordinates
> + *   number: an identifier containing the number of positions desired.  It is
> +       modified to contain the number of positions found.
> + *   pos_check: an expression that determines if position (x, y) is valid.
> + *   max_count: the maximum number of times a random algorithm should be
> +       used before the structured algorithm is used.  The random algorithm
> +       may give duplicate coordinates, so use max_count==0 if you need all
> +       distinct coordinates. */
> +#define RAND_POS_CHECKED(x_arr, y_arr, number, pos_check, max_count)         
>  \
> +{                                                                            
>  \
> +  int *_x_arr = (x_arr); /* if x_arr is "x", it'll conflict down below */    
>  \
> +  int *_y_arr = (y_arr);                                                     
>  \

In general I think we should use "struct map_position" more. This may
such a place.

        Raimar

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