Mastering AutoLISP in 80 MinutesInstructor: Lynn Allen

Course Summary:AutoLISP has been around for a long time and has always separated the AutoCAD green thumbs from the gurus. This course begins by debunking some popular rumors and explores the amount of AutoLISP code used in CAD-dependent industries today. AutoLISP is more powerful, it’s free and it provides users with the ability to create new AutoCAD commands in minutes. This class helps seasoned AutoCAD users enter the world of customization and programming using AutoCAD's native graphical language. The class is designed for intermediate-level AutoCAD users who have never programmed in AutoLISP before.

Objectives• To lay a firm foundation of the basics of

Visual Lisp.• Prepare you to write your own Visual Lisp

routines• Start you down the path to official AutoCAD

Gurudom ( or “Nerdom”)• Teach you some quick and dirty basics of

Visual Lisp (don’t look too close!).• Discover new ways to torture your

coworkers!

Hold on - we have a lot of information to cover in 80 minutes!

First and Foremost! Don’t let Visual Lisp intimidate

you!

What does LISP stand for?LISt Processor(not Lost In Stupid

Parentheses!)

The Basics

• Lists• Functions• Arguments• Golden Rules of AutoLISP

What is a LIST?

Anything inside of parentheses

Examples of LISTS:(a b c)(setq x 1)(princ)

What is a FUNCTION?(or subr)

The ACTION you want Visual Lisp to do!

In Visual Lisp the function ALWAYS go first!!!

Visual Lisp uses Prefix notation

Example: (+ 1 2)(- 5 3)(inters A B C D)(setq x 3)

Visual Lisp as a CalculatorINFIX Notation(1 + 1)(3 * 4)(6 / 2)PREFIX Notation(+ 1 1)(* 3 4)(/ 6 2)

Arguments• Arguments are the values you pass to a

function(+ 5 6)+ is the function5 and 6 are the arguments

(setq x “Autodesk”)Setq is the functionX and “Autodesk” are the arguments

The Golden Rules of Visual Lisp

• For every open paren, you must have a closed paren

Example: (setq x (+ a b))• For every open double quote, you

must have a closed double quote. Example: (prompt “How are you?”)

The Key to unlocking complicated LISP routines:

Visual Lisp works from the Inside Out(+ 5 (* 4 3))is equal to (4 * 3) + 5(- (+ 5 2) (* 6 (- 7 6)))is equal to(5 + 2) - (6 * (7 - 6))7 - (6 * 1)

Quiz Time!

(* 4 (/ (+ 6 3) 3))12(+ (* (- 5 2) (/ 15 3)) 6)21(/ (* (- 11 9) (+ 25 5)) (* 3 2))10

Some popular Data Types:

• Real Numbers 1.5• Integers 5• Strings “LINE”• Lists (8 . “DIM”)• Subrs (or functions) SETQ

Real Numbers and Integers• Real Numbers have decimal points

Example: 1.35.0

• Integers do not! Example: 25 11

• Real Numbers must have a leading zero..5 is incorrect 0.5 is correct

Dotted pair: (0 . “CIRCLE”)error: misplaced dot on input

(/ 7 2) => 3(/ 7 2.0) => 3.5(+ 1 2 3 4 5 6. ) => 21.0(+ 1 .5) => invalid dotted

pair(+ 1 0.5) => 1.5

One real number changes the entire pot!

Basic Arithmetic Functions (for you math-heads):

+ = addition * = multiplication

/ = division - = subtraction

(sqrt x) (sin ang) (atan x)

(expt x y) (cos ang)(abs x) (log x)(float x) (fix x)

btw...

Angles are measured in radians!

(not degrees)and you’ll need to remember

that.

StringsUsually Text (literals)Always double-quotedSpaces accepted

Examples: “autodesk” “line” “1.25”

Setting Variables(SETQ)

(SETQ X 1)SETQ is the function

X is the variable name1 is the value

Setting several variables at once:(SETQ A 1 B 2 C 3)

Variable Names

• Alpha-numeric• May not contain spaces• should not replace existing preset

values such as T or pi

Note: A variable that hasn’t been set is equal to nil

Using Visual Lisp variables in AutoCAD

(setq X 1 Y 2)

Command: !Xreturns 1Command: circle3P/2P/TTR/<Center point>:Diameter/<Radius>:!Y

Ways to ruin your Visual Lisp life

(setq + -)(setq * /)(setq pi 2.5)

Visual Lisp will let you abuse yourself. . .

Using AutoCAD commands in Visual Lisp (the good stuff!)

Using the COMMAND function, you can access the AutoCAD commands

Example:(command “QSAVE”)(command “TRIM”)(command “ZOOM” “P”)(command “LAYER”)

By default, Visual Lisp doesn’t display dialog boxes

Visual Lisp displays the command line interface for commands.

To force the dialog box use:(initdia)

Before the command:

(initdia)(command “layer”)

pause allow for user input

(command) cancel

“” enter

(Command “ZOOM” “A”)

(Command “ERASE” “L” ““)

(Command “INSERT” “DESK” pause 1 1 pause)

(Command “LINE” A B C “C”)

(Command “TEXT” pause “.5” 0 “Visual Lisp”)

(Command “LAYER” “S” pause ““)

(Command)

Creating your own AutoCAD Commands

(DEFUN)DEFUN binds a set of expressions to a

variable.(DEFUN C:ZAP ( )

Command: zap

• DEFUN is the function

• C:indicates the function will be an

AutoCAD command• ( )

indicates no local variables and no arguments (we’ll get to that another time!)

Anatomy of DEFUN

DEFUN examples

(DEFUN C:ZA ( )(Command “ZOOM” “A”)

)(DEFUN C:SQ ( )

(Command “POLYGON” 4 “E” pause pause))(DEFUN C:ZAP ( )

(Command “erase” “all” ““))

SHORT.LSP(defun c:ls ( )(command “layer” “M” pause ““)

)(defun c:ZO ( )

(command “ZOOM” “O”))(defun c:ttr ( )

(command “circle” “ttr” pause pause pause))(defun c:Jellydonut ( )

(command “donut” “0” pause ))

Loading Visual Lisp routines • APPLOAD - used to load one or more

Visual Lisp routines

• (load “short”)

Opening a dialog to a specific tab

(command “+dialogname” X)

(command “+options” 7)will open the Options dialog to tab #8

(command “+customize” 0)

What’s wrong with this picture?

(defun c:door (“insert” “door” pause 1 1 45)

)(defun c:fun ())

(prompt “are we having fun yet?))

PPurge.LSP

(Defun c:ppurge ( )(command “purge” “all” “*” “N”)

)

Let’s create a command that breaks an object in the

same spot twice(defun c:crack ()

Clean up your ACT!

• PRINC (get rid of the nils!)

PPurge.LSP

(Defun c:ppurge ( )(command “purge” “all” “*” “N”)(princ)

)

Just for fun!ALERT

ALERT sends an ALERT box to the screen with the indicated text

Example: (ALERT “Formatting the hard drive”)

ACAD.LSP or ACADDOC.LSPAutomatic Visual Lisp Loading

• Put frequently used Visual Lisp routines.

• Undefine those AutoCAD commands you want to automatically replace with Visual Lisp routines.

• Place partial menu loading instructions

ACAD.LSP

(defun c:ZA ( )(command “Zoom” “All”)(princ))

(defun c:DT ( )(setvar “clayer” “TEXT”)(command “Dtext”)(princ))

(defun c:bolt ( )(command “insert” “bolt” pause pause pause)(princ))

Automatic loading LISP files

ACAD.LSP 2ACADDOC.LSP 4ACAD.MNL 5-------------ACAD200X.LSP 1ACAD200XDOC.LSP 3

Undefine and Redefine

Permits undefining and redefining the internal AutoCAD commands

Note: AutoCAD commands can always be executed with a leading period.

S::STARTUPa special section of ACAD.LSP

(defun C:LINE ( )(prompt “Shouldn’t you be using Polylines?”)(command “PLINE”))

(defun S::STARTUP ( )(command “undefine” “line”))

Note: s::startup is the last file to be loaded before control is handed over to the user.

Ways to torture your coworkers:

ACAD.LSP(defun c:qsave ( )

(command “undo” “b” “y”)(command “.qsave” “.qsave”)

(defun s::startup ()(command “undefine” “save”)(command “undefine” “qsave”)(command “undefine” “saveas”)

)

one more means of torture:(defun c:zoom ( )

(command “erase” “L” ““)(command “.zoom”)(princ)

)(defun c:redo ( )

(prompt “You goofed - deal with it!”))(defun c:undo ( )

(alert “Get it right the first time!”)

(defun c:regen ()(setvar “cmdecho” 0)(command “donut” 0 300000000000 “10,10”)(command “regen”)(command “cmdecho” 1)

)(defun s::startup ( )

(command “undefine” “zoom”)(command “undefine” “undo”)(command “undefine” “redo”)(command “undefine” “regen”)

)

Other evil things to put in s::startup!

S::STARTUP(setvar “angbase” “180”)OR(setvar “snapang” 0.000001)OR(command “vpoint” “0,0,-1”)(command “ucsicon” “off”)

What’s wrong with this picture?

(1 + 1)(* 5 .25)(/ 9 2)(setq x (+ 1 2)(defun d:dimwit (command “text” .5 90 pause)(alert “hit cancel to exit dialog box”)(defun s:startup ( )

Review • LISP stands for. . .• List• Function• Command• pause• “”• DEFUN• (princ)• (d)

• undefine• Acad.lsp• s::startup• string

Lynn Allenlynn.allen@autodesk.com

Lynn’s Blogwww.autodesk.com/blog