Use of Lua in Lab Devices

Sample & Assay Technologies
Use of Lua in Lab Devices
Claus Kühnel, Daniel Zwirner, QIAGEN Instruments AGJanuary 2015
Lua is a powerful,
light-weight programming
language designed for
extending applications.
The language engine is
accessible as a library,
having a C API which
allows the application to
exchange data with Lua
programs and also to
extend Lua with C
functions.
Lua is also used as a
general-purpose,
stand-alone language
through the simple
command line interpreter
provided.

2
Initial Situation
2
Origin of Lua
Lua is designed, implemented, and maintained by
a team at PUC-Rio, the Pontifical Catholic
University of Rio de Janeiro in Brazil.
Lua was born in 1993 and raised in Tecgraf,
formerly the Computer Graphics Technology
Group of PUC-Rio.
LabLua was founded on May 2004 by Prof.
Roberto Ierusalimschy.
Lua is now housed at LabLua, a laboratory of
the Department of Computer Science of PUC-
Rio.
"Lua" (pronounced LOO-ah) means "Moon" in
Portuguese.

3
Initial Situation
3
Initial Situation
Robotic Hardware (HAL)
movexy(x,y) ….
Biological
Protocol
Protocol
Interpreter ….
Robotic Platform

4
• To execute “biological protocols” we need an
protocol interpreter as a layer over the HAL
• Should we develop the 1001. proprietary
interpreter now?
• Searching for a suitable solution leads us to Lua
• A Friday afternoon was enough for installation
and first tests
• Culture shock for the proprietary fraction
Initial Situation

5
• Lua is a powerful, fast, lightweight, embeddable
scripting language.
• Lua combines simple procedural syntax with
powerful data description constructs based on
associative arrays and extensible semantics.
• Lua is dynamically typed, runs by interpreting
byte code for a register-based virtual machine,
and has automatic memory management with
incremental garbage collection, making it ideal
for configuration, scripting, and rapid
prototyping.
What is Lua?

6
• Lua is a proven, robust language used in
applications like Adobe's Photoshop Lightroom,
World of Warcraft & Angry Birds.
• Lua is fast, portable, embeddable
• Lua is powerful (but simple)
• Lua is small. Under Linux, the Lua interpreter
built with all standard Lua libraries takes 182 KB
and the Lua library takes 244 KB.
• Lua is well documented
• Lua is free open-source software, distributed
under the well-known MIT license
• Runs on all common operating systems
Why choose Lua?

7
Lua Documentation

8
Installing Lua (to get a playground)
Lua for Windows
Lua for Windows (LfW) combines Lua binaries, Lua libraries with a
Lua-capable editor in a single install package for the MS Windows
operating system.
LfW contains everything you need to write, run and debug Lua scripts
on Windows. A wide variety of libraries and examples are included
that are ready to use with MS Windows.
https://code.google.com/p/luaforwindows/
Lua for Linux (Debian)
apt-get install lua5.1
apt-get install lua5.1-0-dev
http://ckuehnel.ch/dokuwiki/doku.php?id=lua_on_bananapi

10
Some Lua code
function p(a)
io.write(a .. ", type is " .. type(a) .. "n")
end
a = 123.45
p(a)
-> 123.45, type is number
a = "hello"
p(a)
-> hello, type is string
a = 123+ "12"
p(a)
-> 135, type is number

12
Returning multiple variables
function f(a,b)
return a, a*b, 5
end
print(f(1,2))
-> 1 2 5
a,b,c = f(3,4)
print(a,b,c)
-> 3 12 5
t = {1,2}
print(f(unpack(t)))
-> 1 2 5

14
Variable number of arguments
function f(a,b, ...)
print(a,b, unpack(arg))
end
print(f(1,2))
-> 1 2
print(f(1,2,3))
-> 1 2 3
print(f(1,2, "Hi", " there"))
-> 1 2 Hi there

15
Set of functions that allow C to interact with Lua
• Functions to read and write Lua global variables
• Functions to call Lua functions
• Functions to register C functions within Lua
Stack-based parameter passing
C Interface API

16
Embedding Lua:
• Lua is packed as a library.
• The application calls lua_open to create and
initializes a Lua state.
• When the application is finished running Lua script it
calls lua_close to finalize and destroy Lua state.
Extending Lua:
• The Lua API supports the extension of Lua state by
the possibility to call C functions from Lua scripts.
Embedding Lua vs. Extending Lua

17
Lua Stack – LIFO principle
C-> Lua Lua -> C
void lua_pushnil() lua_isnil()
void lua_pushboolean() int lua_toboolean
void lua_pushnumber() double lua_tonumber
void lua_pushstring() const char* lua_tostring
void lua_pushlstring() size_t lua_strlen
void lua_gettable
void lua_settable

18
Lua Stack – Pushing elements
void lua_pushnil (lua_State *L)
void lua_pushboolean (lua_State *L, int bool);
void lua_pushnumber (lua_State *L, double n);
void lua_pushlstring (lua_State *L, const char *s, size_t length);
void lua_pushstring (lua_State *L, const char *s);

19
Lua Stack – Query elements
int lua_toboolean (lua_State *L, int index)
double lua_tonumber (lua_State *L, int index)
const char * lua_tostring (lua_State *L, int index)
size_t lua_strlen (lua_State *L, int index);

20
Lua Stack – other stack operations
void lua_pop (lua_State *L, int number)
int lua_gettop (lua_State *L)
void lua_settop (lua_State *L, int index)
void lua_pushvalue (lua_State *L, int index)
void lua_remove (lua_State *L, int index)
void lua_insert (lua_State *L, int index)
void lua_replace (lua_State *L, int index);

21
Enhancing Lua by C functions
http://ckuehnel.ch/dokuwiki/doku.php?id=lua_erweiterung
Embedding Lua in a C application
http://ckuehnel.ch/dokuwiki/doku.php?id=lua_embedding

22
Wrapper
SWIG is a software development tool that connects
programs written in C and C++ with a variety of high-level
programming languages.
http://www.swig.org/
tolua is a tool that greatly simplifies the integration of
C/C++ code with Lua. Based on a cleaned header
file, tolua automatically generates the binding code to
access C/C++ features from Lua
http://webserver2.tecgraf.puc-rio.br/~celes/tolua/
Look for examples to both wrappers in our book.

23
Lua in a Lab Device
HAL
movexy(x,y) ….
GUI
movexy(x,y) ….
Lua VM
….
Robotic Platform
Lua enhanced
by C/C++
functions (HAL)
Lua embedded
in C/C++
application (GUI)

INSTRUMENT
init()…
24
Lua in a Lab Device – some code
HAL
init()
GUI
pushButtonInitPressed() ….
LuaVM
run()… luaopen_cube() …
Robotic Platform
Lua embedded
in C/C++
application (GUI)
Lua enhanced
by C/C++
functions (HAL)
Code sample:http://ckuehnel.ch/dokuwiki/doku.php?id=lua_lab_device

Use of Lua in Lab Devices

More Related Content

What's hot

Viewers also liked

Similar to Use of Lua in Lab Devices

Recently uploaded

Use of Lua in Lab Devices