AutoLISP basics for automation in AutoCAD - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a function named 'square' that takes one argument.

AutoCAD

(defun [1] (x) (* x x))

Drag options to blanks, or click blank then click option'

Acircle

Barea

Cline

Dsquare

Attempts:

3 left

💡 Hint

Common Mistakes

Using a function name unrelated to the task like 'circle' or 'line'.

Forgetting to put the function name after defun.

The defun keyword defines a function. Here, the function name should be square to match the task.

2fill in blank

medium

Complete the code to prompt the user for a number and store it in variable 'num'.

AutoCAD

(setq num ([1] "Enter a number: "))

Drag options to blanks, or click blank then click option'

Aprint

Bsetq

Cgetint

Ddefun

Attempts:

3 left

💡 Hint

Common Mistakes

Using print which only displays text.

Using setq inside itself incorrectly.

The getint function prompts the user to enter an integer number.

3fill in blank

hard

Fix the error in the code to correctly calculate the area of a circle with radius 'r'.

AutoCAD

(setq area (* 3.14159 [1] [2]))

Drag options to blanks, or click blank then click option'

Api

Bradius

Carea

Dr

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable name that does not exist like 'radius' or 'pi'.

Using the same blank for different variables.

The radius variable is named r. It must be used twice to calculate area = π * r * r.

4fill in blank

hard

Fill both blanks to create a list of points with x and y coordinates.

AutoCAD

(setq points (list (list [1] [2]) (list 3 4)))

Drag options to blanks, or click blank then click option'

A1

B2

Cx

Dy

Attempts:

3 left

💡 Hint

Common Mistakes

Using variable names instead of numbers.

Swapping the order of x and y.

The first point has coordinates (1, 2). So the blanks should be filled with 1 and 2.

5fill in blank

hard

Fill all three blanks to define a function that returns the sum of two numbers a and b.

AutoCAD

(defun [1] ([2] [3]) (+ a b))

Drag options to blanks, or click blank then click option'

Aadd

Ba

Cb

Dsum

Attempts:

3 left

💡 Hint

Common Mistakes

Using a function name that does not match the operation.

Using parameter names different from those in the sum.

The function name is add. The parameters are a and b to match the sum expression.

Practice

1. What is the main purpose of using AutoLISP in AutoCAD?
(defun) is often used to define what?

easy

A. To export drawings to other formats

B. To manually draw shapes faster

C. To automate repetitive tasks by defining functions

D. To change the color of objects automatically

Solution

1. Step 1: Understand AutoLISP purpose

   AutoLISP is designed to automate tasks in AutoCAD to save time and reduce errors.

2. Step 2: Recognize (defun) usage

   (defun) defines a function that can be run as a command to automate tasks.

3. Final Answer:

   To automate repetitive tasks by defining functions -> Option C

4. Quick Check:

   Automation = Functions with (defun) [OK]

Hint: AutoLISP automates tasks using functions with defun [OK]

Common Mistakes:

• Thinking AutoLISP changes colors automatically
• Confusing manual drawing speed with automation
• Assuming AutoLISP exports files

2. Which of the following is the correct syntax to define a function named drawSquare in AutoLISP?

easy

A. defun drawSquare () (command "RECTANGLE")

B. (defun drawSquare [] (command "RECTANGLE"))

C. (defun drawSquare () command "RECTANGLE")

D. (defun drawSquare () (command "RECTANGLE"))

Solution

1. Step 1: Recall correct function syntax

   AutoLISP functions start with (defun functionName () ...) using parentheses for parameters.

2. Step 2: Check command usage inside function

   The (command "RECTANGLE") is correctly inside the function body.

3. Final Answer:

   (defun drawSquare () (command "RECTANGLE")) -> Option D

4. Quick Check:

   Correct parentheses and command call = (defun drawSquare () (command "RECTANGLE")) [OK]

Hint: Use parentheses () for parameters in defun [OK]

Common Mistakes:

• Using square brackets [] instead of parentheses
• Missing parentheses around defun
• Omitting parentheses around command

3. What will be the output when running this AutoLISP code?

(defun c:test ()
  (command "LINE" '(0 0) '(10 0) "")
  (princ "Line drawn")
)

medium

A. Draws a line from (0,0) to (10,0) and prints 'Line drawn'

B. Nothing happens because function is not called

C. Draws a circle instead of a line

D. Syntax error due to incorrect quotes

Solution

1. Step 1: Analyze the function definition

   The code uses (defun c:test () ...) to define a command named TEST, but does not call or execute it.

2. Step 2: Understand command and output

   Running this code only defines the function. No line is drawn, and no message is printed because the body is not executed. To run it, type TEST or (c:test).

3. Final Answer:

   Nothing happens because function is not called -> Option B

4. Quick Check:

   defun defines, does not run [OK]

Hint: defun defines functions/commands; they must be called to execute [OK]

Common Mistakes:

• Thinking function runs automatically without calling
• Confusing quotes causing syntax errors
• Assuming wrong command draws circle

4. Identify the error in this AutoLISP function:

(defun c:drawLine ()
  (command "LINE" (0 0) (10 10) "")
  (princ "Done")
)

medium

A. Points should be quoted lists, not bare numbers

B. Missing closing parenthesis for defun

C. Command name should be lowercase

D. princ cannot print strings

Solution

1. Step 1: Check point format in command

   AutoLISP requires points as quoted lists like '(0 0), not bare numbers (0 0).

2. Step 2: Verify parentheses and commands

   Parentheses are balanced, command name case is not an error, and princ prints strings correctly.

3. Final Answer:

   Points should be quoted lists, not bare numbers -> Option A

4. Quick Check:

   Points need quotes for lists [OK]

Hint: Use single quotes for coordinate lists '(x y) [OK]

Common Mistakes:

• Using unquoted coordinates causing errors
• Assuming case sensitivity for commands
• Thinking princ can't print strings

5. You want to create an AutoLISP function that draws a rectangle with width 20 and height 10 starting at point (5,5). Which code correctly automates this task?

hard

A. (defun c:drawRect ()
(command "RECTANGLE" '(5 5) '(25 15))
(princ "Rectangle drawn")
)

B. (defun c:drawRect ()
(command "RECTANGLE" (5 5) (20 10))
(princ "Rectangle drawn")
)

C. (defun c:drawRect ()
(command "RECTANGLE" '(5 5) '(20 10))
(princ "Rectangle drawn")
)

D. (defun c:drawRect ()
(command "RECTANGLE" '(0 0) '(20 10))
(princ "Rectangle drawn")
)

Solution

1. Step 1: Calculate rectangle corner points

   Starting at (5,5), width 20 means x=25, height 10 means y=15, so opposite corner is (25 15).

2. Step 2: Check correct point format and command

   Points must be quoted lists '(x y). (defun c:drawRect () (command "RECTANGLE" '(5 5) '(25 15)) (princ "Rectangle drawn") ) uses correct points and syntax.

3. Final Answer:

   (defun c:drawRect () (command "RECTANGLE" '(5 5) '(25 15)) (princ "Rectangle drawn") ) -> Option A

4. Quick Check:

   Correct points and quotes = (defun c:drawRect () (command "RECTANGLE" '(5 5) '(25 15)) (princ "Rectangle drawn") ) [OK]

Hint: Calculate corner points, use quoted lists '(x y) [OK]

Common Mistakes:

• Using unquoted points causing errors
• Using width/height as points instead of coordinates
• Starting rectangle at wrong point