# 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.

%[https://twitter.com/vphreak/status/1412134613611204608?s=20]

On Twitter,  [@stephenjohnlimb](https://twitter.com/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](https://twitter.com/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!

%[https://lisp-lang.org/]

## 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

%[https://en.wikipedia.org/wiki/Format_(Common_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](https://www2.cs.sfu.ca/CourseCentral/310/pwfong/Lisp/1/tutorial1.html) 

## 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

%[https://gist.github.com/sweeneyapps/45caf1ff0feda7afdf170d08436591da]

## 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.