AutoLISP Tutorial 12 : Text Comparison

Welcome to this tutorial on text comparison using AutoLISP! One of the foundational skills in programming is the ability to compare values. In this guide, you’ll be introduced to the basics of how to take two pieces of text input from a user and determine if they are the same or different. By the end, you’ll have a simple, yet powerful tool at your disposal and a deeper understanding of conditionals in AutoLISP.

AutoLISP Tutorial 12 : Text Comparison

In this exercise, you’ll develop a program that prompts the user to input two text strings. The program should then evaluate whether the two entered text strings are identical or not and notify the user accordingly.


  1. Start by creating a function that will be initiated by typing a specific command in AutoCAD.
  2. The program should first prompt the user to enter a text string.
  3. Then, it should ask for a second text string.
  4. After obtaining both strings, the program should determine whether they are identical.
  5. The user should be informed if the texts are identical or not.

Remember to conclude the function to ensure it terminates cleanly.

Use the conditional if function to check the equality of two strings.

Remember, understanding the logic behind the process is as essential as the code itself.

Solution to the Text Comparison Problem in AutoLISP

Understanding how to compare texts is a foundational concept in many programming languages, including AutoLISP. This solution will guide you through creating a simple AutoLISP program that compares two user-entered text strings. Let’s dive in!

The Program:

(defun C:tuto12 (/ str1 str2)
(setq str1 (getstring “\nEnter the first text: “))
(setq str2 (getstring “Enter the second text: “))
(if (= str1 str2)
(princ “The text are identical”)
(princ “The text are not identical”)

Line-by-line Explanation:

(defun C:tuto12 (/ str1 str2):
This begins our function definition. The function’s name is C:tuto12. We declare two local variables, str1 and str2, which will store the text strings entered by the user.

(setq str1 (getstring “\nEnter the first text: “)):
This line prompts the user to enter the first text. The entered text is then stored in the str1 variable.

(setq str2 (getstring “Enter the second text: “)):
Similarly, this line asks the user for the second text string and assigns it to the str2 variable.

(if (= str1 str2):
Here, we use the if function to test if str1 is identical to str2.

(princ “The text are identical”):
This line will execute if the condition above (the two texts being identical) is true. It informs the user that the two texts are the same.

(princ “The text are not identical”):
If the condition is not met (the texts aren’t the same), this line will execute, notifying the user that the texts differ.

This final line ensures a clean exit from the function, returning the last evaluated expression to the AutoCAD command line.

This program offers a straightforward way to understand conditional statements in AutoLISP. With practice, you’ll be able to build more complex functionalities using these foundational concepts!

Conclusion to the Text Comparison Tutorial in AutoLISP

Congratulations on completing the text comparison tutorial! You’ve now taken a significant step in understanding how conditionals work in AutoLISP. With the knowledge gained, you’re better equipped to handle a variety of programming scenarios. Remember, the key to mastering any programming language is consistent practice and exploration. So, keep experimenting and happy coding!