Modularizing Your Code (AutoLISP)

As a result of the work you did in Lesson 3, your gpmain.lsp file was getting rather large. This is not a problem for Visual LISP, but it is easier to maintain the code if you split things up into files containing logically related functions. It is also easier to debug your code. For example, if you have a single file with 150 functions, a single missing parenthesis can be difficult to find.

In the tutorial, the files will be organized as follows:

Tutorial file organization
File name	Contents
gp-io.lsp	All input and output (I/O) functions) such as getting user input. Also contains the AutoLISP code required for the dialog box interface you will be adding.
utils.lsp	Includes all generic functions that can be used again on other projects. Also contains load-time initializations.
gpdraw.lsp	All drawing routines—the code that actually creates the AutoCAD entities.
gpmain.lsp	The basic C:GPath function.

To split gpmain.lsp into four files

1. Create a new file, then cut and paste the following functions from gpmain.lsp into the new file:
   • gp:getPointInput
   • gp:getDialogInput

   Save the new file in your working directory as gp-io.lsp.

2. Create a new file, then cut and paste the following functions from gpmain.lsp into the new file:
   • Degrees->Radians
   • 3Dpoint->2Dpoint
   • gp:list->variantArray

   Also, at the beginning of the file, insert the lines of code to establish ActiveX functionality (vl-load-com) and commit global variable assignment (*ModelSpace*).

   Save the file as utils.lsp.

3. Create a new file, then cut and paste the following function from gpmain.lsp into the new file:
   • gp:drawOutline

   Save this file as gpdraw.lsp.

4. After stripping the code out of gpmain.lsp, save it and check it. Only the original function, C:GPath, should remain in the file.

Your desktop is starting to get crowded. You can minimize any window within Visual LISP and it stays accessible. Click the Select Window button on the toolbar to choose a window from a list, or click Window from the Visual LISP menu and select a window to view.