This routine may come in handy if you would like to trim or extend lines to an object.

Note: This routine will only modify line objects.

Here’s how:

• TTT <enter> to start
• Select the bounding edge that the lines will either be trimmed at or extended to
• Select the objects that you want to be modified
• <enter> when finished

Note that lines that are crossing the cutting edge will be trimmed and the portion that will be erased is the portion that has the smaller amount of overlap. For lines that are sitting at their midpoint – the side of the line that was drawn first (the first pick point when creating the line) will be kept.

;;; Touch.LSP                                              *
;;; Small routine to align endpoints of lines to an edge.  *
;;; The edge have to be a line.                            *
;;; The routine works by calculating the point of inter-   *
;;; section and change the nearest endpoint to that point  *
;;; 2001 Stig Madsen, no rights reserved                   *
;;; modified by qjchen, the edge line can be line or polyline *
;
;GREAT for PROJECTING LINES FOR ELEVATIONS !!!!!!!!!!!
;
(defun C:Ttt (/ cmd ent entl spt ept sset a lent lentl lspt lept lint)
  (vl-load-com)
  (setq cmd (getvar "CMDECHO"))
  (setvar "CMDECHO" 0)
  (command "UNDO" "Begin")
  (while (not ent)
    (setq ent (car (entsel "Select edge line: ")))
    (if ent
      (progn
	(setq entl (entget ent))
      )
    )
  )
  (if ent
    (progn
      (redraw ent 3)
      (prompt "\nSelect lines to touch edge: ")
      (setq sset (ssget '((0 . "LINE")))
	    a 0
      )
      (if sset
	(repeat (sslength sset)
	  (setq lentl (entget (setq lent (ssname sset a)))
		lspt (cdr (assoc 10 lentl))
		lept (cdr (assoc 11 lentl))
	  )
	  (setq entttt (ssname sset a))
	  (setq lint (nth 0 (x_intlst ent entttt acExtendOtherEntity)))
	  (if lint
	    (progn

	      (if (< (distance lint lspt) (distance lint lept))
		(entmod (subst
			  (cons 10 lint)
			  (assoc 10 lentl)
			  lentl
			)
		)
		(entmod (subst
			  (cons 11 lint)
			  (assoc 11 lentl)
			  lentl
			)
		)
	      )
	    )
	  )
	  (setq a (1+ a))
	)
	(princ "\nNo objects found")
      )
      (redraw ent 4)
    )
    (princ "\nNo edge selected")
  )
  (setvar "CMDECHO" cmd)
  (command "UNDO" "End")
  (princ)
)

;;; by kuangdao at xdcad
(defun x_intlst (obj1 obj2 param / intlst1 intlst2 ptlst)

  (if (= 'ENAME (type obj1))
    (setq obj1 (vlax-ename->vla-object obj1))
  )
  (if (= 'ENAME (type obj2))
    (setq obj2 (vlax-ename->vla-object obj2))
  )
  (setq intlst1 (vlax-variant-value (vla-intersectwith obj1 obj2 param)))
  (if (< 0 (vlax-safearray-get-u-bound intlst1 1))
    (progn
      (setq intlst2 (vlax-safearray->list intlst1))
      (while (> (length intlst2) 0)
	(setq ptlst (cons (list (car intlst2) (cadr intlst2) (caddr intlst2))
			  ptlst
		    )
	      intlst2 (cdddr intlst2)
	)
      )
    )
  )
  ptlst
)