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AutoCAD: Secrets Every User Should Know

Chapter 8 - AutoLISP by Example: Getting Started

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Key Topics

- Entity Selection and Manipulation

- Constructing New Points

- String Conversion and Manipulation

- Debugging and Troubleshooting Techniques

- Annotating and Error-Trapping

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AutoLISP Based on LISP from 1950s Good User Language

Can use AutoCAD commands Can use AutoCAD variables

VLISP Added AutoCAD 200 Uses AutoCAD Commands

VBA and VB.NET

C++

Programming Tools

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Writing Text Editor Visual LISP Editor NO Word Processors

Saving ASCII Text File .LSP extension ACADDOC.lsp Loads in Each Drawing ACAD.lsp Loads Only When AutoCAD Fires Up

Saving AutoLISP Programs

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Three ways to load AutoLISP Type it at the command line

or copy/paste to the command line

Load a text file that contains AutoLISP code

(load “program.lsp”) APPLOAD Startup Suite

Use the load function of the Visual LISP editor

Loading Programs

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Start Visual LISP Editor VLISP or VLIDE ToolsAutoLISPVisual

LISP Editor

Four Windows Text editor: type your program

(more than one can be open) Visual LISP console: type

variable names or pieces of code

Trace window: use while debugging

Build Output window: warnings and error messages

Visual LISP Editor

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Visual LISP - Color Coding

Color Used for

Blue AutoLISP functions like /, DEFUN, and SETQ

Magenta Strings, which are always between quotation marks

Black User-created items, such as program variables and function names

Green Integer values

Teal Real numbers, which must have a decimal point

Maroon on gray Comments, which are preceded by a semicolon

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VLISP Tools

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AutoLISP by Example

Or format like this:

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Program Structure

• Programs Contain AutoLISP Functions DEFUN, SETVAR, +, and -

• Function Name Is Preceded by an Opening Parenthesis (defun, or (command, or (+

• Balance Parentheses

• Separate Atoms with Spaces or Quotation Marks

• Functions Are Followed by Arguments, if They’re Necessary

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Breaking Down the Code

(defun c:00() Defun is an AutoLISP expression

C: means “command” not drive

(setvar “osmode” 4143) Setvar is an AutoLISP expression

“osmode” is a system variable

4143 is a bit sum setting

) Closes opening parenthesis in line 1

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Bit Sum 1, 2, 4, 8, 16, 32, 64, 128, etc.

Why 4143?

End, Mid, Cen, Nod, Int, and Ext as running osnaps

Type OSMODE at the command line

Returns 4143

1+2+4+8+32+4098 = 4143.

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Building on the Basics

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System Variables

Over 550 in AutoCAD 2007

Examples: APERTURE; AUPREC; LUPREC

Some saved in drawing, others in Registry

(getvar “aperture”) (setvar “aperture” 3)

Environment Variables – Operating System

Examples: “MaxHatch” "HideSystemPrinters"

Saved in Registry

(getenv “MaxHatch”) (setenv “MaxHatch” “100000000”)

Background - Variables

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Program Variables

Defined by the programmer using SETQ

Global (defun C:MID ()

Retain their value when program terminates

Useful for debugging

Often Changed to Local

Can be used to create a persistent default value

Local (defun C:MID (/ os ap m)

Return to nil when program terminates

!variable at command line to get value

Background - Variables

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SETQ

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Deciphering the Code

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Creating New Coordinates

Structural Lumber Symbol

Get Point1 and Point 2 from User

Create Point3 from X of Point 1 and Y of Point2

Create Point4 from X of Point 2 and Y of Point1

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Creating New Coordinate Points - LIST

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Creating New Points - POLAR

Dimension Between Walls

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Creating New Points - POLAR

Polar pt Angle Distance

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Calculations

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Calculations - More

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Calculations in Programs

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Angles

Radians vs. Degrees

AutoLISP uses Radians

Radian: included angle of arc with length of 1

Degrees Radians

0 0

90 Pi/2

180 Pi

270 3pi/2

360 2pi

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Angles

Radian Problems

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Angles

Radians vs. Degrees Conversion Functions

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Transparent Commands

Two Methods

‘I2M will work for many command functions

Call non-command functions as Lisp

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Combining Programs

SSECT and RC

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Ten Basic Rules

1. Save as ASCII.

2. Use Equal Number of Opening and Closing Parens.

3. DEFUN Means Define Function; C:ZX Is a Command.

4. Balance Quotation Marks.

5. Backslash Is a Control Character: \\ or / for Folders.

6. Leave Space After Forward Slash for Local Variables.

7. \n Controls New Line in Prompt and Is Lowercase.

8. Use Semicolons for Comments.

9. Get Values at Beginning; Use SETQ to Save Them.

10. Don't Get Discouraged!

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Automatic Loading

APPLOAD Startup Suite

Any LSP program placed by user

ACAD.lsp

Loads when AutoCAD starts IF in the path

Loads in subsequent drawings IF ACADLSPASDOC=1

ACADDOC.lsp

Loads with each drawing IF in the path

(There are some others, but you probably don’t want to mess them up)

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Automatic Loading

Startup Functions