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Lisp is an expression-oriented language. Unlike most other languages, no distinction is made between “expressions” and “statements;” all code and data are written as expressions. When an expression is evaluated, it produces a value (in Common Lisp, possibly multiple values), which then can be embedded into other expressions. Each value can be any data type.

Download software: Lispbox IDE

Cost: Free

Instructions to setup software:

Hardware requirements: PC, Mac

Operating systems supported: Win, Mac, Linux

Difficulty level: 4 out of 5


1. After downloading the IDE from lispbox extract the contents into a file on your computer.

2. Copy and paste this Lisp code into your favorite text editor. Windows notepad works fine.

(defun convert ()
(format t "Enter Fahrenheit ")
  (LET (fahrenheit)
    (SETQ fahrenheit (read fahrenheit))    	
          (LET (celsius) 
               (SETQ celsius (round(*(- fahrenheit 32.0)(/ 5.0 9.0))) )	  
               (format t "Celsius is ~a" celsius)	
               (if (<= celsius 0) (format t " Pack Long Underwear ~C" #\linefeed))
               (if(>= fahrenheit 100) (format t " Remember to Hydrate ~C"  #\linefeed))
  (format t "~C"  #\linefeed)
  (format t "Would you like to do another calculation? 1=yes 2=no ")
  (LET (repeat)
     (SETQ repeat (read repeat))
          (if (= repeat 1) (convert))

3. Save the File as “lisp_example.lisp” in the root of the folder you created in step 1.

4. Start Lispbox by running lispbox.bat (Windows) / (Linux) / Emacs (OS X).

5. When you start up the Common LISP environment, you should see a prompt, which means that LISP is waiting for you to enter a LISP expression. To load the file you created in step 3 type the following expression including the parenthesis, (load “lisp_demo.lisp”) or use the CTRL+C CTRL+L shortcode.

6. Once your program is loaded you can execute it with the following command, (convert)

7. Try several different temperatures by looping through the program with 1 for yes.


1. Change the temperatures used in the decisions — change the lower temperature from 60 to 30 degrees, for example. Make sure you change it in two places! Save the file and refresh the browser (or restart the web page), and enter new numbers — did the answers change at the new temperature?

2. Create a new temperature range from 30 to 60 degrees and have it display – “Bring hat and gloves!”

3. Change the wording of the phrases.


Common Lisp — Getting started with Lisp.


Notepad++ is a great free text editor designed specifically for programmers. Check it out here.

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