What Is a LISP Routine in AutoCAD?

by

A LISP routine in AutoCAD is a set of instructions written in the LISP programming language that can automate tasks and enhance the functionality of AutoCAD software. LISP stands for “LISt Processing” and was developed in the late 1950s by John McCarthy as a way to manipulate symbolic expressions.

Why Use LISP Routines in AutoCAD?

LISP routines provide several benefits to AutoCAD users, including:

  • Automation: LISP allows you to automate repetitive tasks, reducing manual effort and saving time.
  • Customization: With LISP, you can customize commands and create new ones tailored to your specific needs.
  • Extended Functionality: LISP routines can extend the capabilities of AutoCAD by adding new features or enhancing existing ones.

How to Create a LISP Routine

To create a LISP routine in AutoCAD, follow these steps:

Step 1: Open the Visual LISP Editor

In AutoCAD, go to the “Tools” menu, select “AutoLISP,” and choose “Visual LISP Editor.” This will open the Visual LISP Integrated Development Environment (IDE).

Step 2: Write Your Code

In the Visual LISP Editor, you can write your LISP code. The code consists of a series of expressions enclosed in parentheses. Each expression performs a specific action or calculation.

(defun c:myCommand ()
  (command "._line" pause)
  (command "._circle" pause)
)

In this example, the code defines a new command named “myCommand” that draws a line and then a circle in AutoCAD.

Step 3: Save the LISP File

After writing your code, save the LISP file with a .lsp extension. It is recommended to save the file in a location that AutoCAD can easily access, such as the support folder.

Step 4: Load the LISP Routine

To use the LISP routine in AutoCAD, you need to load it. There are two ways to load a LISP routine:

  • Manual Loading: Type “appload” in the AutoCAD command line, browse for your .lsp file, and click “Load. “
  • Automatic Loading: You can configure AutoCAD to automatically load specific LISP routines when it starts.

    To do this, go to the “Tools” menu, select “AutoLISP,” and choose “Load Application.” Browse for your .lsp file and click “Load.” The routine will now load every time you launch AutoCAD.

Using LISP Routines in AutoCAD

Once you have loaded a LISP routine, you can execute it by typing its command name in the command line or by creating a button or menu item that triggers the command.

Tips for Writing Effective LISP Routines

To create efficient and well-performing LISP routines, consider these tips:

  • Use Descriptive Variable Names: Choose meaningful names for variables and functions to improve code readability.
  • Add Error Handling: Include error handling mechanisms to handle unexpected situations gracefully.
  • Test Your Code: Thoroughly test your LISP routines to ensure they work as intended and handle different scenarios correctly.

By leveraging the power of LISP routines, you can streamline your workflow and enhance your productivity in AutoCAD. With practice and experimentation, you can create sophisticated routines that automate complex tasks, ultimately saving you time and effort.