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Lua is a powerful, efficient, lightweight, embeddable scripting language. It supports procedural programming, object-oriented programming, functional programming, data-driven programming, and data description. "Lua" (pronounced LOO-ah) means "Moon" in Portuguese. As such, it is neither an acronym nor an abbreviation, but a noun. From the Lua web site is at https:///lua.org .

The Wikipedia article at https://en.wikipedia.org/wiki/Lua_(programming_language) has a good background and short introduction to Lua.

Lua - from Portuguese for "moon" - scripting language.

The programming/scripting language Lua is named for Portuguese name for "moon" as it was developed in Brazil in the 1990's.

The Lua web site is at https:///lua.org .

Lua was created and still maintained by Roberto Ierusalimschy.

Roberto Ierusalimschy is the leading architect of the Lua programming language, driving its development since its inception in 1993. He is an Associate Professor of Computer Science at PUC-Rio (the Pontifical Catholic University of Rio de Janeiro), where he works with programming-language design and implementation. (from the Amazon biography author page for him)

The English word "moon" is related to the Greek word for "month". The lunar/moon cycle was used as the basis for a month.

• The Latin word mensis = "month".
• The English word "menstrual" is from the menstrualis = "monthly" which comes from mensis = "month".
• The modern Greek word μήνας (MEE-nas) = "month".

But Greek has other words for "moon".

• The modern Greek word σελήνη (seh-LEE-nee) = "moon", from the brightness of the moon.
• The modern Greek word φεγγάρι (fehn-GA-ree) = "moon", from the shimmering of the moon.
• The Latin word luna = "month" has roots in the last part of the Greek word σελήνη (seh-LEENEE) = "moon"
• The Portuguese word for "moon" is "lua", for which a popular computer scripting language Lua (developed in Brazil) is named.

φεγγάρι = moon
μήνας = month

Lua is a scripting language written in ANSI C, and is popular in many game systems as well as in the following:

• SciTE editor
• Logitech G-13 gaming keypad and G- gaming keyboard.
• Redis NoSQL database
• Creative Zen X-Fi2
• Celestia (astronomy, looked and tried it briefly)
• LuaTeX (I use Lua for custom formatting)
• Lego Mindstorms NXT (via 3rd party software)

Here are some more applications that use Lua (that I have not actually used but may at some time).

• Angry Birds (and many other games)
• Apache HTTP server
• Foldit (protein folding science-oriented game)
• MediaWiki (used on Wikipedia) as a template language
• MySQL Workbench
• WireShark, nmap, NetBSD (security scripting)
• Rockbox (open source digital audio player firmware)
• SAS (integrates Lua with the PROC)
• Torch (open source deep learning software)
• Vim editor
• NUT - Network UPS tools
• and many other places (see Wikepedia article)

My use of Lua includes the following.

• Reading and processing off-line email folders containing XML feeds for newspaper headlines, conference announcements, etc.
• Finding minimum instances of Simpson's Paradox (in statistics).
• Developing the LCS (Longest Common Subsequence) algorithm - dual of MED (Minimum Edit Distance) algorithm and then using it in application.
• Developing a system to process every keystroke in the SciTE editor and providing a simple and yet sophisticated and extensible menu system.

I have two talks at the 2012 Lua Workshop in Reston, Virginia, on November 29-30, 2012.

• Incrementally developing and implementing Hirschberg's longest common subsequence algorithm using Lua
• Adding an Lua-based integrated character-based menu system into the SciTE editor

The web site is https://www.lua.org/wshop12.html (as of 2019-09-01).

The video and PDF for those talks is on than web site.

The LPEG (Lua Parsing Expression Grammar) adds a simple and yet powerful parsing capability to Lua.

I have used it for the following.

• Parsing EBNF (Extended Backus Naur Form) grammars, including EBNF in EBNF to create syntax diagrams, etc.
• Parsing subset of EBNF grammars to create a corresponding complex and tedious to make and check XTD (XML Type Definition) file.
• Parsing logical and arithmetic expressions.
• Parsing and converting expressions to PostScript postfix form expressions.
• Managing custom parts of a sophisticated text formatting and programming system at the format level.
• Programming and hooking the Logitech G-13 gaming keyboard for programming applications.

The file type of a Lua program file is lua.

The following Linux command(s) create/edit a hello program in the your home directory using the nano text editor.

Create the following program text in the editor that will output the text "Hello world"

To exit with save, remember to press Ctrl-X, then "y" (for yes) and Enter to exit.

The following Linux command(s) run the program.

The output should be as follows.

Let us look at a program to implement to algorithm for decimal to binary conversion.

The routine toBinary1 takes as input a value and returns the string representation in binary (base 2)

The first part of the program will use the hard-coded value of 156.

The second part will use a loop to output the decimal values and binary representations of the values from 0 to 16.

Here is the Lua code.
function toBinary1(x1) local s2 = "" if x1 == 0 then s2 = "0" else while x1 ~= 0 do local r1 = x1 % 2 x1 = math.floor(x1 / 2) s2 = r1 .. s2 end end return s2; end x1 = 156 s1 = toBinary1(x1) print(string.format("Value %dd in binary is %sb.\n",x1,s1)) print("\n") for i1=0,16 do s1 = toBinary1(i1) print(string.format("%dd == %sb\n",i1,s1)) end

Here is the output of the Lua code.
Value 156d in binary is 10011100b. 0d == 0b 1d == 1b 2d == 10b 3d == 11b 4d == 100b 5d == 101b 6d == 110b 7d == 111b 8d == 1000b 9d == 1001b 10d == 1010b 11d == 1011b 12d == 1100b 13d == 1101b 14d == 1110b 15d == 1111b 16d == 10000b

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