;;;
;;;
;;;>	Author:	Henry C. Francis
;;;>		425 N. Ashe St.
;;;>		Southern Pines, NC 28387
;;;>		http://paracadd.com
;;;>		All rights reserved.
;;;
;;;>		COPYRIGHT: 6-21-99
;;;>		   EDITED: 09-06-2005
;;;
(DEFUN ttarc_error (msg / )
  (setq *error* old_ttarcerror)
  (setvar "osmode" old_osmodes)
  (princ "\nERROR: ")
  (princ msg)
  (princ "\n")
  (princ)
)
(DEFUN C:TTARC ()
  (setq old_ttarcerror *error*)
  (setq old_osmodes (getvar "osmode"))
  (setvar "osmode" 0)
  (setq frst_tan (nentselp "\nSelect first tangent"))
  (setq scnd_tan (nentselp "\nSelect second tangent"))
  (setq frst_edef (entget (car frst_tan)))
  (setq scnd_edef (entget (car scnd_tan)))
  (setq frst_sav frst_edef)
  (setq scnd_sav scnd_edef)
  (if ureal
    nil
    (load "ureal" "\nFile UREAL.LSP bot loaded! ")
  ) ;_ end of if
  (if (eq (cdr (assoc 0 frst_edef)) "VERTEX")
    (progn (while (not (equal (cdr (assoc 0 frst_edef)) "SEQEND"))
             (setq frst_edef (entget (entnext (cdr (assoc -1 frst_edef)))))
           ) ;_ end of while
           (setq frst_edef (entget (entnext (cdr (assoc -2 frst_edef)))))
           (while (not (equal frst_edef frst_sav))
             (setq frst_edef (entget (entnext (cdr (assoc -1 frst_edef)))))
           ) ;_ end of while
           (setq frst_pnt1 (list (cadr (assoc 10 frst_edef)) (caddr (assoc 10 frst_edef)) 0)
                 frst_pnt2 (list (cadr (assoc 10 (entget (entnext (cdr (assoc -1 frst_edef))))))
                                 (caddr (assoc 10 (entget (entnext (cdr (assoc -1 frst_edef))))))
                                 0
                           ) ;_ end of list
           ) ;_ end of setq
    ) ;_ end of progn
    (progn (if (not (equal (cdr (assoc 0 frst_edef)) "LINE"))
             (progn (princ "\nFirst entity not a polyline or line!") (setq abort_attarc T))
             (setq frst_pnt1 (list (cadr (assoc 10 frst_edef)) (caddr (assoc 10 frst_edef)) 0)
                   frst_pnt2 (list (cadr (assoc 11 frst_edef)) (caddr (assoc 11 frst_edef)) 0)
             ) ;_ end of setq
           ) ;_ end of if
    ) ;_ end of progn
  ) ;_ end of if
  (if (eq (cdr (assoc 0 scnd_edef)) "VERTEX")
    (progn (while (not (equal (cdr (assoc 0 scnd_edef)) "SEQEND"))
             (setq scnd_edef (entget (entnext (cdr (assoc -1 scnd_edef)))))
           ) ;_ end of while
           (setq scnd_edef (entget (entnext (cdr (assoc -2 scnd_edef)))))
           (while (not (equal scnd_edef scnd_sav))
             (setq scnd_edef (entget (entnext (cdr (assoc -1 scnd_edef)))))
           ) ;_ end of while
           (setq scnd_pnt1 (list (cadr (assoc 10 scnd_edef)) (caddr (assoc 10 scnd_edef)) 0)
                 scnd_pnt2 (list (cadr (assoc 10 (entget (entnext (cdr (assoc -1 scnd_edef))))))
                                 (caddr (assoc 10 (entget (entnext (cdr (assoc -1 scnd_edef))))))
                                 0
                           ) ;_ end of list
           ) ;_ end of setq
    ) ;_ end of progn
    (progn (if (not (equal (cdr (assoc 0 scnd_edef)) "LINE"))
             (progn (princ "\nSecond entity not polyline or line!") (setq abort_attarc T))
             (setq scnd_pnt1 (list (cadr (assoc 10 scnd_edef)) (caddr (assoc 10 scnd_edef)) 0)
                   scnd_pnt2 (list (cadr (assoc 11 scnd_edef)) (caddr (assoc 11 scnd_edef)) 0)
             ) ;_ end of setq
           ) ;_ end of if
    ) ;_ end of progn
  ) ;_ end of if
  (cond (abort_attarc (setq abort_arc nil))
        ((or (eq (angle frst_pnt1 frst_pnt2) (angle scnd_pnt1 scnd_pnt2))
             (eq (angle frst_pnt1 frst_pnt2) (angle scnd_pnt2 scnd_pnt1))
         ) ;_ end of or
         (princ "\nSegments are parallel! ")
        )
        (T
         (setq tarc_rad (ureal 1 "" "\nRadius for tangent arc? " tarc_rad))
         (setq vrtx_pnt (inters frst_pnt1 frst_pnt2 scnd_pnt1 scnd_pnt2 nil))
         (setq frst_pkpnt (inters (cadr frst_tan)(polar(cadr frst_tan)(+(angle frst_pnt1 frst_pnt2)(/ pi 2.0))tarc_rad)frst_pnt1 frst_pnt2 nil))
         (setq frst_clpt1 (polar frst_pkpnt (+(angle frst_pnt1 frst_pnt2)(* pi 0.5))tarc_rad))
         (setq frst_clpt2 (polar frst_pkpnt (+(angle frst_pnt1 frst_pnt2)(* pi 1.5))tarc_rad))
         (IF (<(distance frst_clpt1 (cadr frst_tan))(distance frst_clpt2 (cadr frst_tan)))
           (setq frst_clpt frst_clpt1)
           (setq frst_clpt frst_clpt2)
         )
         (setq scnd_pkpnt (inters (cadr scnd_tan)(polar(cadr scnd_tan)(+(angle scnd_pnt1 scnd_pnt2)(/ pi 2.0))tarc_rad)scnd_pnt1 scnd_pnt2 nil))
         (setq scnd_clpt1 (polar scnd_pkpnt (+(angle scnd_pnt1 scnd_pnt2)(* pi 0.5))tarc_rad))
         (setq scnd_clpt2 (polar scnd_pkpnt (+(angle scnd_pnt1 scnd_pnt2)(* pi 1.5))tarc_rad))
         (IF (<(distance scnd_clpt1 (cadr scnd_tan))(distance scnd_clpt2 (cadr scnd_tan)))
           (setq scnd_clpt scnd_clpt1)
           (setq scnd_clpt scnd_clpt2)
         )
         (setq cntr_pnt (inters frst_clpt (polar frst_clpt (angle frst_pnt1 frst_pnt2) tarc_rad) scnd_clpt (polar scnd_clpt (angle scnd_pnt1 scnd_pnt2) tarc_rad) nil))
         (setq frst_pnt0 (inters frst_pnt1 frst_pnt2 cntr_pnt (polar cntr_pnt (+(angle frst_pnt1 frst_pnt2)(* pi 0.5)) tarc_rad)nil))
         (setq scnd_pnt0 (inters scnd_pnt1 scnd_pnt2 cntr_pnt (polar cntr_pnt (+(angle scnd_pnt1 scnd_pnt2)(* pi 0.5)) tarc_rad)nil))
         (command "arc" "c" cntr_pnt frst_pnt0 scnd_pnt0)
         (command "arc" "c" cntr_pnt scnd_pnt0 frst_pnt0)

;;;         (cond ((and (eq vrtx_pnt frst_pnt1) (eq vrtx_pnt scnd_pnt1))
;;;                (setq ang_tend1 (- (angle vrtx_pnt frst_pnt2) (angle vrtx_pnt scnd_pnt2)))
;;;               )
;;;               ((and (eq vrtx_pnt frst_pnt1) (eq vrtx_pnt scnd_pnt2))
;;;                (setq ang_tend2 (- (angle vrtx_pnt frst_pnt2) (angle vrtx_pnt scnd_pnt1)))
;;;               )
;;;               ((and (eq vrtx_pnt frst_pnt2) (eq vrtx_pnt scnd_pnt2))
;;;                (setq ang_tend3 (- (angle vrtx_pnt frst_pnt1) (angle vrtx_pnt scnd_pnt1)))
;;;               )
;;;               ((and (eq vrtx_pnt frst_pnt2) (eq vrtx_pnt scnd_pnt1))
;;;                (setq ang_tend4 (- (angle vrtx_pnt frst_pnt1) (angle vrtx_pnt scnd_pnt2)))
;;;               )
;;;               (T (setq ang_tend (- (angle vrtx_pnt frst_pnt1) (angle vrtx_pnt scnd_pnt1))))
;;;         ) ;_ end of cond
;;;         (cond ((> ang_tend pi) (setq ang_tend (- (* 2 pi) ang_tend)))
;;;               ((< ang_tend (- 0 pi)) (setq ang_tend (+ (* 2 pi) ang_tend)))
;;;         ) ;_ end of cond
;;;         (setq cntr_dis (/ tarc_rad (sin (/ (abs ang_tend1) 2.0000))))
;;;         (tpntcalc)
;;;         (setq cntr_dis (/ tarc_rad (sin (/ (abs ang_tend2) 2.0000))))
;;;         (tpntcalc)
;;;         (setq cntr_dis (/ tarc_rad (sin (/ (abs ang_tend3) 2.0000))))
;;;         (tpntcalc)
;;;         (setq cntr_dis (/ tarc_rad (sin (/ (abs ang_tend4) 2.0000))))
;;;         (tpntcalc)
        )
  ) ;_ end of cond
  (setq *error* old_ttarcerror)
  (setvar "osmode" old_osmodes)
  (princ)
) ;_ end of DEFUN

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