Delete exact duplicate objects

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;;; ============================================================================
;;; CXDUPDEL - Delete exact duplicate objects
;;; Version 1.0.0
;;; CADXChange LISP tools - https://cadxchange.net/resources/lisp/cxdupdel
;;; Tested in: AutoCAD (full version). Other programs that run AutoLISP may work but are not tested.
;;; Copyright (c) CADXChange. Free for personal and commercial use; do not resell or
;;; republish it as a collection. Terms: https://cadxchange.net/legal/lisp-terms
;;; ============================================================================

;; A string that is the same for two entities exactly when they are duplicates of each other: every data group
;; except the handle, owner and reactor groups, with numbers rounded to 6 decimals.
(defun cx:dup-signature (ed / out)
  (foreach g ed
    (if (not (member (car g) '(-1 -2 -3 5 102 105 330 331 360)))
      (setq out (cons (strcat (itoa (car g)) "="
                              (cond ((= (type (cdr g)) 'STR) (cdr g))
                                    ((= (type (cdr g)) 'INT) (itoa (cdr g)))
                                    ((= (type (cdr g)) 'REAL) (rtos (cdr g) 2 6))
                                    ((= (type (cdr g)) 'LIST) (apply 'strcat (mapcar (function (lambda (v) (strcat (rtos v 2 6) ","))) (cdr g))))
                                    (T "")))
                      out))))
  (cx:join (reverse out) ";"))

;; Erase every entity in NAMES that has an exact duplicate earlier in the list. Returns how many were erased.
(defun cx:dup-run (names / rows prev n)
  (setq n 0)
  (setq rows (cx:sort (mapcar (function (lambda (e) (cons (cx:dup-signature (entget e)) e))) names)
                      (function (lambda (a b) (< (car a) (car b))))))
  (foreach r rows
    (if (and prev (= (car prev) (car r)))
      (progn (entdel (cdr r)) (setq n (1+ n)))
      (setq prev r)))
  n)

(defun c:CXDUPDEL ( / *error* cx:sv ss n)
  (setq *error* cx:err)
  (if (setq ss (cx:pick "\nSelect objects (type ALL for the whole drawing): " nil))
    (progn
      (cx:start '(("CMDECHO" . 0)))
      (setq n (cx:dup-run (cx:ss->list ss)))
      (princ (strcat "\n" (itoa n) " duplicate object(s) deleted."))
      (cx:end)))
  (princ))


;;; ---- Shared helpers (used by the command above; identical in every CADXChange tool) ----

(defun cx:join (lst delim / out)
  (setq out "")
  (foreach s lst
    (setq out (if (= out "") s (strcat out delim s))))
  (if lst out ""))

;; Merge sort of LST with PRED (a function of two items that is true when the first goes first).
(defun cx:sort (lst pred / half a b out)
  (cond
    ((or (null lst) (null (cdr lst))) lst)
    (T
     (setq half (/ (length lst) 2) a nil b lst)
     (repeat half (setq a (cons (car b) a) b (cdr b)))
     (setq a (cx:sort (reverse a) pred) b (cx:sort b pred) out nil)
     (while (and a b)
       (if (apply pred (list (car b) (car a)))
         (setq out (cons (car b) out) b (cdr b))
         (setq out (cons (car a) out) a (cdr a))))
     (append (reverse out) a b))))

;; Close the undo step and put the system variables back.
(defun cx:end ()
  (foreach v cx:sv (setvar (car v) (cdr v)))
  (command "_.UNDO" "_End")
  (setq cx:sv nil)
  (princ))

;; Error handler: restores everything, stays quiet on Esc.
(defun cx:err (msg)
  (if (> (getvar "CMDACTIVE") 0) (command))
  (cx:end)
  (if (and msg (not (wcmatch (strcase msg) "*BREAK*,*CANCEL*,*EXIT*")))
    (princ (strcat "\nError: " msg)))
  (princ))

;; Use the objects already selected, or ask the user to select; FILTER is an ssget filter list or nil.
(defun cx:pick (msg filter / ss)
  (setq ss (if filter (ssget "_I" filter) (ssget "_I")))
  (if (null ss)
    (progn
      (princ msg)
      (setq ss (if filter (ssget filter) (ssget)))))
  ss)

;; Save the system variables in VARS ((name . value) ...), set them, and open one undo step.
;; The caller declares cx:sv as a local so the saved values live exactly as long as the command.
(defun cx:start (vars)
  (setq cx:sv (mapcar (function (lambda (v) (cons (car v) (getvar (car v))))) vars))
  (command "_.UNDO" "_Begin")
  (foreach v vars (setvar (car v) (cdr v)))
  (princ))

;; Selection set to a list of entity names.
(defun cx:ss->list (ss / i out)
  (setq i 0)
  (if ss
    (repeat (sslength ss)
      (setq out (cons (ssname ss i) out)
            i   (1+ i))))
  (reverse out))

(princ "\nCXDUPDEL loaded. Type CXDUPDEL to start.")
(princ)

More commands: Clean-up

• CXBYLAYERSet color, linetype and lineweight back to ByLayer
• CXZEROLENFind and delete zero-length lines and polylines
• CXEMPTYTXTFind and delete empty text
• CXFONTCHKList text styles whose font file is missing
• CXFONTSUBReplace one font file by another in all text styles
• CXPURGEPurge the drawing until nothing more goes
• CXDELTYPEDelete every object of the type you pick
• CXDIMRESETReset typed-over dimension text to the measured value
• CXOBJCOUNTCount the objects by type