Exploring LISP programming

Exploring LISP programming

As of today, I have never seen any LISP programming language before. I am writing this article while I am learning LISP, why am I doing this? It is because I made a joke on a tweet about JavaScript (ECMAScript 2015) keywords.

On Twitter, @stephenjohnlimb replied and suggested LISP avoid those JavaScript keywords. I told him that I am going to try LISP programming tomorrow, so that's why I am here writing about the experience.

Getting Started

Right now, I'm at google.com looking for a LISP programming resource. @mohjb said that Lisp was the 2nd language (after assembly). Oh boy!

I have been googling around and trying another bunch of stuff and then finally, I found this simple site to learn LISP!

Installing Common Lisp

I am on my M1 MacBook Pro and already have brew.sh installed. HomeBrew is awesome because it makes my life easier installing programs to run in the terminal.

Inside the terminal, I only have to type in: brew install sbcl and then bang! It's installed! Also, we have to install a package manager for LISP which is called quickLISP.

curl -o /tmp/ql.lisp http://beta.quicklisp.org/quicklisp.lisp

sbcl --no-sysinit --no-userinit --load /tmp/ql.lisp \
  --eval '(quicklisp-quickstart:install :path "~/.quicklisp")' \
  --eval '(ql:add-to-init-file)' \
  --quit

Creating Hello World in LISP

I am going to read the tutorial and my goal is to print out Hello World from LISP! so I can start somewhere here. I'm opening up the VS Code app to start writing my first Hello World on LISP!

;;; helloworld.lisp
;;; by Paul Sweeney Jr
;;;

;; This is a comment
;;

(format t "Hello, world!") ; this is inline comment

I am saving this as helloworld.lisp

Running LISP

I am not sure, what's next? So, I just type in man sbcl to read the manual on the terminal. I figured out that I can type in sbcl --script helloworld.lisp to run my very first LISP program!

Format string

I want to do some math for my LISP program. So, I googled format lisp to find out how to print out numbers. I found the answer and it is (format t "~d" 3) to output a number. You can dive into wiki about format text on LISP

Let do some math

Lisp does have some math functions to use. Those are a few basic examples here.

(+ 3 6) ; 9
(- 1 5) ; -4
(* 3 3) ; 9
(/ 10 2) ; 5

This is where I learned about math at this website: www2.cs.sfu.ca

Adding defined functions

I am adding my own defined function to my LISP program!

;; functions
;;

(defun add (x y)
  (format t "~d" (+ x y))
)

(defun sub (x y)
  (format t "~d" (- x y))
)

(defun multiply (x y)
  (format t "~d" (* x y))
)

(defun divide (x y) 
  (format t "~d" (/ x y))
)

(add 1 2)
(sub 1 4)
(multiply 3 3)
(divide 10 2)

Result

I ran the program and here is the result but it's not what I am expecting.

Hello, world!3-395%

I googled on how to add linefeed to my program... here is it! (format t "~d ~%") and whoa! I did it and it works after some struggling.

(format t "~d + ~d = ~d ~%" (values x) (values y) (+ x y))

Final Program

Final Result

vphreak@Pauls-MBP lisp % sbcl --script helloworld.lisp
Hello, world! 
1 + 2 = 3 
1 - 4 = -3 
3 * 3 = 9 
10 / 2 = 5

Wrapping up

So far, I learned how to run LISP program on my computer and output Hello, World!, also added some defined functions with some math. I will come back to LISP someday if I want to learn more.

 
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