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        Fri, 11 Sep 2015 14:41:23 -0700 (PDT)
Date: Sat, 12 Sep 2015 00:41:21 +0300
From: "Vladimir Zhbanov (vzhbanov AT gmail DOT com) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
To: geda-user AT delorie DOT com
Subject: Re: [geda-user] About reinventing the wheel, and how to avoid it
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On Fri, Sep 11, 2015 at 04:06:36PM +0200, Roland Lutz wrote:
...
> Imagine the following SQL query:
> 
>     DELETE FROM objects WHERE radius = 0.;
> 
> Using Xorn as an example, you could either iterate over all objects, looking
> for circles and arcs wth a matching radius, and delete these objects:
> 
>     xorn_object_t *objects;
>     size_t count;
>     unsigned int i;
> 
>     xorn_get_objects(rev, &objects, &count);
> 
>     for (i = 0; i < count; i++) {
>         xorn_obtype_t type = xorn_get_object_type(rev, objects[i]);
> 
>         if (type == xornsch_obtype_circle &&
>             xornsch_get_circle_data(rev, objects[i])->radius == 0.)
>             xorn_delete_object(rev, objects[i]);
> 
>         if (type == xornsch_obtype_arc &&
>             xornsch_get_arc_data(rev, objects[i])->radius == 0.)
>             xorn_delete_object(rev, objects[i]);
>     }
> 
>     free(objects);

And that's an impenetrable code for the same in Guile:

  (use-modules (geda page))

  ; Checks if the OBJECT is a circle or an arc with zero radius
  (define (zero-radius-object? object)
    (or
      (and (circle? object) (= (circle-radius object) 0))
      (and (arc?    object) (= (arc-radius    object) 0))))

  (apply page-remove! (active-page)
         (filter
           zero-radius-object?
           (page-contents (active-page))))

Just about reinvention of the wheel. :-/

Cheers,
  Vladimir