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LISP and groups

How can we handle named and unnamed groups?

If you want to do operations within a group you can use what is documented here: http://adndevblog.typepad.com/autocad/2012/12/how-to-add-a-group-in-a-selection-set-from-an-autolisp-function.html. A cached version:

(defun selgrp (grpname)
   ;; grpname is the group name, it accepts
   ;; unnamed groupnames, such as *A1
   (setq grp (dictsearch (namedobjdict) "ACAD_GROUP"))
   (setq a1 (dictsearch (cdr (assoc -1 grp)) grpname))
   (setq ss (ssadd))
   (while (/= (assoc 340 a1) nil)
      (setq ent (assoc 340 a1))
      (setq ss (ssadd (cdr ent) ss))
      (setq a1 (subst (cons 0 "") ent a1))
   )
   ss
)

• http://www.cadtutor.net/forum/showthread.php?12647-Getting-a-list-of-groups-used-in-autocad

• Bounding boxes: http://forums.autodesk.com/t5/visual-lisp-autolisp-and-general/the-smallest-rectangle-enclosing-selected-set-of-objects/td-p/3791519/highlight/true

• http://forums.autodesk.com/t5/visual-lisp-autolisp-and-general/get-min-max-coordinates-of-a-set-of-lines/td-p/4675359