get started with lua - hackference 2016

Get started with

Etiene Dalcol @etiene_d

@etiene_dHackference 2016

@etiene_d


A Lua MVC web framework sailorproject.org

http://lualadies.org

@etiene_dHackference 2016 luaconf.com

http://luaconf.com


What’s Lua

Why Lua

Key Concepts


• Dynamic duck-typed language • Multi-paradigm

• procedural, OO, functional

• Garbage collection • Coroutines • First-class functions • Lexical scoping • Proper tail calls • MIT License

What is Lua?


Why Lua?

Powerful.


Why Lua?Size

(docs included)

First-class functions+

Lexical scoping +

Metatables

Native C API

276 Kb

Object Orientation

Ada, Fortran, Java, Smalltalk, C#, Perl,

Ruby etc.+


Simple.Powerful.

Why Lua?


_G _VERSION assert collectgarbage dofile error getmetatable ipairs load loadfile next pairs pcall print rawequal rawget rawlen rawset require select setmetatable tonumber tostring type xpcall bit32.arshift bit32.band bit32.bnot bit32.bor bit32.btest bit32.bxor bit32.extract bit32.lrotate bit32.lshift bit32.replace bit32.rrotate bit32.rshift

coroutine.create coroutine.resume coroutine.running coroutine.status coroutine.wrap coroutine.yield debug.debug debug.getuservalue debug.gethook debug.getinfo debug.getlocal debug.getmetatable debug.getregistry debug.getupvalue debug.setuservalue debug.sethook debug.setlocal debug.setmetatable debug.setupvalue debug.traceback debug.upvalueid debug.upvaluejoin io.close io.flush io.input io.lines io.open io.output io.popen io.read io.stderr io.stdin io.stdout io.tmpfile io.type io.write

file:close file:flush file:lines file:read file:seek file:setvbuf file:write math.abs math.acos math.asin math.atan math.atan2 math.ceil math.cos math.cosh math.deg math.exp math.floor math.fmod math.frexp math.huge math.ldexp math.log math.max math.min math.modf math.pi math.pow math.rad math.random math.randomseed math.sin math.sinh math.sqrt math.tan math.tanh

os.clock os.date os.difftime os.execute os.exit os.getenv os.remove os.rename os.setlocale os.time os.tmpname package package.config package.cpath package.loaded package.loadlib package.path package.preload package.searchers package.searchpath string.byte string.char string.dump string.find string.format string.gmatch string.gsub string.len string.lower string.match string.rep string.reverse string.sub string.upper table.concat table.insert table.pack table.remove table.sort table.unpack

Hackference 2016 @etiene_d

"Since Lua itself is so simple, it tends to

encourage you to solve problems simply."

Ragnar Svensson - Lead Developer at King (Lua Workshop Oct 15 2015)


Fast.Simple.Powerful.

Why Lua?


http://www.humbedooh.com/presentations/ACNA%20-%20mod_lua.odp Introducing mod_lua by Daniel Gruno

http://www.humbedooh.com/presentations/ACNA%20-%20mod_lua.odp


My Reasons

• It looks cool (I heard you could make games with it)

Better


Better Reasons


• It’s made in my home country (In my university to be more precise)



• It’s made in my home country (In my university to be more precise)

• It’s easy to learn

Better Reasons


• The index starts at 1 • There’s no continue • The non-equality operator is ~= • null is nil • Comments are - - • Only nil and false are equivalent to false • Functions can genuinely return multiple values • Variables are global by default • Pattern matching is not regular expression • The concatenation operator is ..

What’s different


Quick idioms

• a, b = b, a

• There’s no ternary operator but you can return x==1 and “yes” or “no”

• The access to local variables is faster than to global local match = string.match


Using Lua: three approaches

Embedded Scripting General-purpose


Getting Lua

• lua.org > download

• OS package manager • apt-get install lua • brew install lua

LuaRocks

• luarocks.org > install

• OS package manager • apt-get install luarocks

http://lua.org


Key Concepts


• The only way to structure data

• Array, dictionary, object, list, queue, module…

• Any value can be a key, except nil and nan

• Behind the scenes: array or hash table

• Passed as reference

• The length operator: #

• pairs(t) x ipairs(t)

Tables Tables Tables


Tables

Header

key value

“x” 9.2

nil

value

100

200

300

nil


• The only way to structure data

• Array, dictionary, object, list, queue, module…

• Any value can be a key, except nil

• Behind the scenes: array or hash table

• Passed as reference

• The length operator: #

• pairs(t) x ipairs(t)

Tables


Tables

local a = { 1, 3, 5, 7, 9}

local sum = 0

for i=1,#a do

sum = sum + a[i]

end

print(sum) -- 25


local a = { 1, 3, 5, 7, 9}

local sum = 0

for i=1,#a do

sum = sum + a[i]

end

print(sum) -- 25

Tables

local a = {}

a[1] = 1

a[2] = 3 -- etc

local sum = 0

for _, x in ipairs(a) do

sum = sum + x

end

print(sum)


local a = { 1, 3, 5, 7, 9}

local sum = 0

for i=1,#a do

sum = sum + a[i]

end

print(sum) -- 25

local point = { x = 10, y = 25}

print(point[“x”], point[“y”]) -- 10 25

print(point.x, point.y) -- 10 25

print(point[x], point[y]) -- nil nil (attention!)

Tables


local a = { 1, 3, 5, 7, 9}

local sum = 0

for i=1,#a do

sum = sum + a[i]

end

print(sum) -- 25

local point = { x = 10, y = 25}

print(point[“x”], point[“y”]) -- 10 25

print(point.x, point.y) -- 10 25

print(point[x], point[y]) -- nil nil (attention!)

-- sets and multisets

local ips = {[“5.101.112.0”] = true, [“213.35.128.0”] = true}

local conns = {[“5.101.112.0”] = 5, [“213.35.128.0”] = 2}

Tables


-- Cipher module

--[[ Based on algorithms/caesar_cipher.lua

by Roland Yonaba ]]

local cipher = {}

local function ascii_base(s)

return s:lower() == s and ('a'):byte() or ('A'):byte()

end

function cipher.caesar( str, key )

return str:gsub('%a', function(s)

local base = ascii_base(s)

return string.char(((s:byte() - base + key) % 26) + base)

end)

end

return cipher

Modules


-- Cipher module


by Roland Yonaba ]]

local cipher = {}



end

function cipher.caesar( str, key ) --cipher.caesar = function(str,key)

return str:gsub('%a', function(s) --cipher["caesar"] = function(str,key)



end)

end

return cipher

Modulespublic


-- Cipher module


by Roland Yonaba ]]

local cipher = {}



end





end)

end

return cipher

Modules

private


-- Cipher module


by Roland Yonaba ]]

local cipher = {}



end





end)

end

return cipher

Modules

local c = require “cipher”

print(c.caesar(“test”,3) -- whvw


• Overload operators

• Override built-in functions such as tostring

• Treat missing fields or intercept new field creation

• Call table as a function

• Metamethods:__add, __sub, __mul, __div, __mod, __pow, __unm, __concat, __len, __eq, __lt, __le, __index, __newindex, __call, __tostring, __ipairs, __pairs, __gc

Metatables


local mt = {}

local function new(r, i)

return setmetatable({ real = r or 0, im = i or 0}, mt)

end

local function is_complex(v)

return getmetatable(v) == mt

end

local function add(c1, c2)

if not is_complex(c1) then

return new(c2.real + c1, c2.im)

elseif not is_complex(c2) then


end

return new(c1.real + c2.real, c1.im + c2.im)

end

local function tos(c)

return tostring(c.real) .. "+".. tostring(c.im) .. "i"

end

mt.__add = add

mt.__tostring = tos

Complex numbers


local mt = {}

local function new(r, i)

return setmetatable({ real = r or 0, im = i or 0}, mt)

end

local function is_complex(v)

return getmetatable(v) == mt

end

local function add(c1, c2)

if not is_complex(c1) then


elseif not is_complex(c2) then


end

return new(c1.real + c2.real, c1.im + c2.im)

end

local function tos(c)

return tostring(c.real) .. "+".. tostring(c.im) .. "i"

end

mt.__add = add

mt.__tostring = tos>local c1 = new(2,3) >print( c1 + 5 ) 7+3i

Complex numbers


local square = { x = 10, y = 20, side = 25 }

function square.move(obj, dx, dy)

obj.x = obj.x + dx

obj.y = obj.y + dy

end

function square:area()

return self.side ^ 2

end

print(square:area()) -- 625

Objects


local square = { x = 10, y = 20, side = 25 }

function square.move(obj, dx, dy)

obj.x = obj.x + dx

obj.y = obj.y + dy

end

function square:area()


end

print(square:area()) -- 625

local square2 = (x = 30, y = 5, side = 10}

print(square.area(square2)) -- 100

Objects


local Square = {}

function Square:new(x, y, side)

local o = { x = x, y = y, side = side}

setmetatable(o, self)

self.__index = self

return o

end

function Square:move(dx, dy)

self.x = self.x + dx

self.y = self.y + dy

end

function Square:area()


end

return Square

Object Orientation


local Square = {}

function Square:new(x, y, side)

local o = { x = x, y = y, side = side}

setmetatable(o, self)

self.__index = self

return o

end

function Square:move(dx, dy)

self.x = self.x + dx

self.y = self.y + dy

end

function Square:area()


end

return Square

local Square = require “square”

local s1 = Square:new(10,20,25)

local s2 = Square:new(30,5,10)

print(s1:area()) -- 625

print(s2:area()) -- 100

Object Orientation

Thank you!

etiene.net github.com/Etiene/

[email protected]

@etiene_d

http://github.com/Etiene/

mailto:[email protected]


Going further


• Hardware • eLua: http://www.eluaproject.net/ • nodemcu: http://nodemcu.com

• Scientific Computing and Machine Learning • SciLua http://www.scilua.org/ • Torch: http://torch.ch • GSL Shell: http://www.nongnu.org/gsl-shell/

Cool tools in Lua

http://nodemcu.com

http://torch.ch


• Game development • Love2D: https://love2d.org/ • Defold: http://www.defold.com/ • Cocos2d: http://www.cocos2d-x.org/ • Corona: https://coronalabs.com

• Web development • (Nginx) OpenResty http://openresty.org • Luvit: https://luvit.io/ • Lapis: http://leafo.net/lapis/ • Sailor: http://sailorproject.org/ • Starlight: http://starlight.paulcuth.me.uk/

Cool tools in Lua

https://love2d.org/

http://www.defold.com/

http://www.cocos2d-x.org/

https://coronalabs.com

http://sailorproject.org/


• IDE • ZeroBrane Studio: http://studio.zerobrane.com/

• Testing • Busted: http://olivinelabs.com/busted/

• Package management • LuaRocks http://luarocks.org

• Misc • Moonscript: http://moonscript.org/ • Awesome Lua:

https://github.com/LewisJEllis/awesome-lua

Cool tools in Lua

http://olivinelabs.com/busted/

http://moonscript.org/

https://github.com/LewisJEllis/awesome-lua


• Community • Lua mail list: http://www.lua.org/lua-l.html • #LuaLang on Twitter • Lua community blog: http://lua.space • Lua’s subreddit: http://reddit.com/r/lua • Lua’s IRC channel: irc.freenode.net #lua

• Books • Programming in Lua: http://www.lua.org/pil/ • Lua Programming Gems: http://www.lua.org/gems/

• Misc • CodeCombat: https://codecombat.com

Resources

http://www.lua.org/lua-l.html

http://lua.space

http://reddit.com/r/lua

http://www.lua.org/pil/

https://codecombat.com

Thank you!

etiene.net github.com/Etiene/

[email protected]

@etiene_d

http://github.com/Etiene/

mailto:[email protected]

get started with lua - hackference 2016

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