;; | ----------------------------------------------------------------------------
;; | GE_Collinear?
;; | ----------------------------------------------------------------------------
;; | Function : Find out if three points are collinear within a given tolerance
;; | Argument : [p1]   - First point
;; |            [p2]   - Second point
;; |            [p3]   - Third point
;; |            [InBetFlag] - In Between flag, if T, then additionally check if
;; |                          'p1' is in between 'p2' and 'p3'.
;; |            [fuzz] - Fuzzy distance
;; | Return   : T if the three points are colinear within the tolerance, else nil
;; | e-mail   : rakesh.rao@4d-technologies.com
;; | Web      : www.4d-technologies.com
;; | ----------------------------------------------------------------------------


(defun GE_Collinear?( p1 p2 p3 InBetFlag fuzz / RetVal OS )

(setq
	OS (getvar "OSMODE")
	RetVal nil
)
(setvar "OSMODE" 0)
(cond
	((not (equal p1 p2 0.001))
		(command "._Ucs" "_3Point" p1 p2 (polar p1 (+ (angle p1 p2) #pb2) 10.0))
	)
	((not (equal p2 p3 0.001))
		(command "._Ucs" "_3Point" p2 p3 (polar p2 (+ (angle p2 p3) #pb2) 10.0))
	)
	(T
		(setq RetVal T)
	)
)

(if (not RetVal)
(progn
	(setq p3 (trans p3 0 1))
	(command "._Ucs" "_Previous")
	(if (<= (abs (cadr p3)) fuzz)
	(progn
		(if InBetFlag
		(progn
			(setq
				p1 (list 0.0 0.0 0.0)
				p2 (list (distance p1 p2) 0.0 0.0)
			)
			(if (MI_InBetween (car p1) (car p2) (car p3))
				(setq RetVal T)
				(setq RetVal nil)
			)
		)
		(setq RetVal T)
		)
	)
	(setq RetVal nil)
	)
))
(setvar "OSMODE" OS)
RetVal
)