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Lua and its Ecosystem (45��)

Fran?ois Perrad
francois.perrad@gadz.org

fperrad@OSDC.fr2011

Overview
? Lua is a powerful, fast, lightweight,
embeddable scripting language.
? from Brazil (PUC-Rio) since 1993
? Open Source, but closed development
? A core team (academic)
? Roberto Ierusalimschy
? Luiz Henrique de Figueiredo
? Waldemar Celes
? MIT License
? A mailing list since 1997
? lastest Workshop on September 8�C9, 2011

fperrad@OSDC.fr2011

History of recent releases

fperrad@OSDC.fr2011

Lua is small
? Reference Manual
? < 100 pages
? Grammar EBNF
? 1 page
? Code size : Sloccount -> 12.5 KLoC of C
? Binary ~150 kB
? 8 types
? nil, boolean, number, string, function, userdata,
thread, table
? 21 keywords
? No builtin function,
? only standard libraries

fperrad@OSDC.fr2011

Lua is portable
? Only C89
? Linux, OSX, Windows
? Android, iOS
? Corona SDK
? eLua runs on the "bare-metal"
? LEGO Mindstorm NXT
? ��

fperrad@OSDC.fr2011

Alternate Implementations
? LuaJIT
? Very fast, full compatible
? LLVM-Lua
? Mochalua
? Java JME
? Jill
? Java JME, JSE

fperrad@OSDC.fr2011

Lua is powerful
? function as first class
? closure
? exception (as library)
? coroutine (as library)
? iterator
? regex (with its own dialect)
? some OO mechanisms (prototype based)
? tail call

fperrad@OSDC.fr2011

Factorial - Loop
function factorial (n)
local a = 1
for i = 1, n, 1 do
a = a * i
end
return a
end

print(factorial(7)) --> 5040

fperrad@OSDC.fr2011

Factorial �C recursive
if n == 0 then
return 1
else
return n * factorial(n-1)
end
end


fperrad@OSDC.fr2011

Factorial - Iter
local function iter (prod, cnt)
if cnt > n then
return prod
else
return iter(cnt*prod, cnt+1)
end
end
return iter(1, 1)
end


fperrad@OSDC.fr2011

Fibonacci - iterator
local function fibo_iterator ()
local x, y = 0, 1
return function ()
local res = x
x, y = y, x+y
return res
end
end

for v in fibo_iterator() do
print(v)
if v >= 144 then break end
end
fperrad@OSDC.fr2011

Fibonacci - Coroutine
local function fibo_generator ()
local x, y = 0, 1
while true do
coroutine.yield(x)
x, y = y, x+y
end
end

local function fibo_iterator ()
return coroutine.wrap(fibo_generator)
end

for v in fibo_iterator() do
print(v)
if v >= 144 then break end
end

fperrad@OSDC.fr2011

Fibonacci �C metamethods
local fibo = setmetatable({
[0] = 0,
[1] = 1,
}, {
__index = function (t, n)
local res = t[n-1] + t[n-2]
t[n] = res -- memoize
return res
end,
__call = function (t, n)
return t[n]
end,
})

for i = 0, 12 do
print(fibo(i))
end

fperrad@OSDC.fr2011

Lua is embeddable / extensible
? Designed to be integrated with software
writen in C

? C API
? Comprehensible
? Well documented
? Stack model

? All standard libraries are built with

? Userdata is a core type and allows
metatable/metamethods

fperrad@OSDC.fr2011

Lua Module Land / Heterogenority
? Build system
? nothing
? Makefile
? CMake
? Documentation
? LuaDoc : �� la JavaDoc
? LuaPOD : with Perl
? QA �C Test
? assert
? lunit : �� la xUnit
? Lunity
? lua-TestMore : �� la Perl (Test Anything Protocol)
? Packaging / Deployment
? LuaDist (CMake)
? LuaRocks

fperrad@OSDC.fr2011

A rockspec sample (plain Lua)
package = 'lua-CodeGen'
version = '0.2.2-1'
source = {
url = 'http://cloud.github.com/downloads/fperrad/lua-CodeGen/lua-codegen-0.2.2.tar.gz',
md5 = '782a40b6ac55ee3077e10f302e301706',
dir = 'lua-CodeGen-0.2.2',
}
description = {
summary = "a template engine",
detailed = [[
lua-CodeGen is a "safe" template engine.
lua-CodeGen enforces a strict Model-View separation.
lua-CodeGen allows to split template in small chunk, and encourages the reuse of them by inheri
lua-CodeGen is not dedicated to HTML, it could generate any kind of textual code.
]],
homepage = 'http://fperrad.github.com/lua-CodeGen',
maintainer = 'Francois Perrad',
license = 'MIT/X11'
}
dependencies = {
'lua >= 5.1',
'lua-testmore >= 0.2.3',
}
build = {
type = 'builtin',
modules = {
['CodeGen'] = 'src/CodeGen.lua',
['CodeGen.Graph'] = 'src/CodeGen/Graph.lua',
},
copy_directories = { 'doc', 'test' },
}

fperrad@OSDC.fr2011

Binding modules
? LuaSocket : socket, http, smtp
? LuaSec : https
? LuaPOSIX
? LuaExpat : XML
? LuaSQL : mysql, postgres, sqlite, ��
? wxLua : wxWidget
? LuaGnome : GTK
? LuaZMQ
? ��

fperrad@OSDC.fr2011

Other modules / projects
? Kepler : web development platform
? Orbit : an MVC web framework
? WSAPI : �� la WSGI, Rack, PSGI/Plack
? Sputnik : a wiki engine
? Lpeg : Parsing Expression Grammars
? LuaJSON
? Lua Lanes - multithreading in Lua
? OiL : an Object Request Broker (CORBA)
?
��

fperrad@OSDC.fr2011

Use case : textadept
? Textadept is a fast, minimalist, and
ridiculously extensible text editor for Linux,
Mac OSX, and Windows
? Lead dev : Mitchell
? started on 2007, 1.0 on Jan 2009
? 2 KLoC of C + 6 KLoc of Lua
? Textadept 4.0 embeds
? Lua 5.1.4
? LPeg 0.9
? LuaFileSystem 1.4.1
? Scintilla 2.28 / GTK+
? MIT License

fperrad@OSDC.fr2011

Use case : wireshark
? Wireshark (Ethereal) is the world's
foremost network protocol analyzer
? > 2 MLoC of C
? Lua can be used to write dissectors,
post-dissectors and taps.
? Lua introduced around 0.99.4
? GPL License

fperrad@OSDC.fr2011

Use case : LuaTeX
? LuaTeX is an extended version of
pdfTeX using Lua as an embedded
scripting language.
? started on 2007
? source size
? 300 KLoC of C
? 200 KLoc of C++
? 10 KLoC of Lua
? GPL License

fperrad@OSDC.fr2011

Use case : awesome
? awesome is an extensible, highly
configurable window manager for X.
? started on 2007
? 10 KLoC of C + 7 KLoC of Lua
? It's extremely fast, small, dynamic
and heavily extensible using the Lua
programming language.
? GPL License

fperrad@OSDC.fr2011

Use case : Redis
? Redis is an open-source, networked, in-
memory, persistent, journaled, key-value
data store
? Lead dev : antirez
? started on 2009
? 30 KLoC of C
? Scripting branch released on May 2011
? Server-side scripting with Lua
? Easy to embed, and FAST
? scripting.c : 500 LoC
? will available with Redis 2.6
? License : BSD

fperrad@OSDC.fr2011

Sponsors
? Adobe
? Photoshop Lightroom
? 40% is written in Lua
? Penlight : A Portable Lua Library
? The workshop 2005 held at Adobe��s
headquarters in San Jos��, California
? SocialMediaPress
? CSTUG
? Oc��
? Printer, copier, plotter
? The workshop 2006 held at Oc��'s R&D
department in Venlo, The Netherlands

fperrad@OSDC.fr2011

Philosophy of Lua

? Mechanisms instead of policies

? Zen of Lua :
? Doing more with less.

fperrad@OSDC.fr2011

Conclusion

? An embeddable scripting language
that is simple, efficient, portable and
lightweight

? supports several paradigm of
programming :
? procedural
? Object-Oriented
? functional
? data-driven

fperrad@OSDC.fr2011

Bibliography / Webography
? www.lua.org
? the Lua 5.1 Reference Manual
? www.luafaq.org
? http://lua-users.org/wiki/
? The evolution of Lua
? Small is Beautiful: the design of Lua
? Lua Short Reference
? Programming in Lua
? Lua programming Gems
? LuaForge (frozen since 2009)

fperrad@OSDC.fr2011

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Lua and its Ecosystem

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