© 2006 Autodesk AutoCAD: Secrets Every User Should Know Chapter 8 - AutoLISP by Example: Getting...

© 2006 Autodesk

AutoCAD: Secrets Every User Should Know

Chapter 8 - AutoLISP by Example: Getting Started

2© 2006 Autodesk

Key Topics

- Entity Selection and Manipulation

- Constructing New Points

- String Conversion and Manipulation

- Debugging and Troubleshooting Techniques

- Annotating and Error-Trapping

3© 2006 Autodesk

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

4© 2006 Autodesk

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

5© 2006 Autodesk

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

6© 2006 Autodesk

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

7© 2006 Autodesk

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

8© 2006 Autodesk

VLISP Tools

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AutoLISP by Example

Or format like this:

10© 2006 Autodesk

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

11© 2006 Autodesk

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

12© 2006 Autodesk

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.

13© 2006 Autodesk

Building on the Basics

14© 2006 Autodesk

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

15© 2006 Autodesk

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

16© 2006 Autodesk

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

30© 2006 Autodesk

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!

31© 2006 Autodesk

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)

32© 2006 Autodesk

Automatic Loading

Startup Functions