Revising the Program Code

Now that you've seen how to use association lists in AutoLISP code, you can use this method in writing the completed version of the gp:getPointInput function. Using the following code, replace or modify the version of gp:getPointInput you previously saved in gpmain.lsp.

;;;--------------------------------------------------------------;

;;;  Function: gp:getPointInput							 ;

;;;--------------------------------------------------------------;

;;;  Description: This function asks the user to select three	;

;;; 		 points in a drawing, which will determine the  ;

;;; 		 path location, direction, and size.			;

;;;--------------------------------------------------------------;

;;;  If the user responds to the get functions with valid data,  ;

;;;  use startPt and endPt to determine the position, length, ;

;;;  and angle at which the path is drawn.					 ;

;;;--------------------------------------------------------------;

;;;  The return value of this function is a list consisting of:  ;

;;;   (10 . Starting Point) ;; List of 3 reals (a point) denoting ;

;;; 					 ;;  starting point of garden path.   ;

;;;   (11 . Ending Point)   ;; List of 3 reals (a point) denoting ;

;;; 					 ;;  ending point of garden path.	 ;

;;;   (40 . Width)		;; Real number denoting boundary	 ;

;;; 					 ;;  width.						 ;

;;;   (41 . Length)		 ;; Real number denoting boundary	 ;

;;; 					 ;;  length.						;

;;;   (50 . Path Angle)	 ;; Real number denoting the angle	;

;;; 					 ;;  of the path, in radians.		 ;

;;;--------------------------------------------------------------;

(defun gp:getPointInput	(/ StartPt EndPt HalfWidth)

  (if (setq StartPt (getpoint "\nStart point of path: "))

	(if	(setq EndPt (getpoint StartPt "\nEndpoint of path: "))

	(if (setq HalfWidth (getdist EndPt "\nhalf-width of path: "))

		 ;; if you've made it this far, build the association list

		 ;; as documented above.  This will be the return value

		 ;; from the function.

		 (list

		 (cons 10 StartPt)

		 (cons 11 EndPt)

		 (cons 40 (* HalfWidth 2.0))

		 (cons 50 (angle StartPt EndPt))

		 (cons 41 (distance StartPt EndPt))

) ) ) ) )

Next, you need to update the main function, C:GPath, in gpmain.lsp. Modify it to look like the following code:

(defun C:GPath (/ gp_PathData)

  ;; Ask the user for input: first for path location and

  ;; direction, then for path parameters.  Continue only if you

  ;; have valid input.  Store the data in gp_PathData.

  (if (setq gp_PathData (gp:getPointInput))

	(if	(gp:getDialogInput)

	(progn

			;; At this point, you have valid input from the user.

			;; Draw the outline, storing the resulting polyline

			;; pointer in the variable called PolylineName.

			(setq PolylineName (gp:drawOutline))

			(princ "\nThe gp:drawOutline function returned <")

			(princ PolylineName)

			(princ ">")

			(Alert "Congratulations - your program is complete!")

		) ;_ end of progn

	 (princ "\nFunction cancelled.")

	) ;_ end of if

	(princ "\nIncomplete information to draw a boundary.")

  ) ;_ end of if

 (princ)							 ; exit quietly

);_ end of defun

If you are copying and pasting the code, add the following comments as a header preceding C:GPath:

;;;**************************************************************;

;;;  Function: C:GPath		The Main Garden Path Function   ;

;;;--------------------------------------------------------------;

;;;  Description: This is the main garden path function. It is a ;

;;; 		 C: function, meaning that it is turned into an ;

;;; 		 AutoCAD command called GPATH. This function	;

;;; 		 determines the overall flow of the garden path ;

;;; 		 program.									 ;

;;;**************************************************************;

;;; The gp_PathData variable is an association list of the form: ;

;;;  (10 . Starting Point) - List of 3 reals (a point) denoting  ;

;;; 					 starting point of the garden path. ;

;;;  (11 . Ending Point)   - List of 3 reals (a point) denoting  ;

;;; 					 endpoint of the garden path.	 ;

;;;  (40 . Width)		- Real number denoting boundary	 ;

;;; 					 width.							 ;

;;;  (41 . Length)		 - Real number denoting boundary	 ;

;;; 					 length.							;

;;;  (50 . Path Angle)	 - Real number denoting the angle of   ;

;;; 					 the path, in radians.			;

;;;  (42 . Tile Size)	- Real number denoting the size	 ;

;;; 					 (radius) of the garden path tiles. ;

;;;  (43 . Tile Offset)	- Spacing of tiles, border to border. ;

;;;  ( 3 . Object Creation Style)								;

;;; 					- Object creation style indicates how ;

;;; 					the tiles are to be drawn.  The	 ;

;;; 					expected value is a string and one  ;

;;; 					one of three values (string case	;

;;; 					is unimportant):					;

;;; 						"ActiveX"					 ;

;;; 						"Entmake"					 ;

;;; 						"Command"					 ;

;;;  ( 4 . Polyline Border Style)								;

;;; 					- Polyline border style determines	;

;;; 					the polyline type to be used for	;

;;; 					path boundary.  The expected value  ;

;;; 					one of the following (string case is;

;;; 					unimportant):					 ;

;;; 						"Pline"						 ;

;;; 						"Light"						 ;

;;;**************************************************************;