Lua as a scripting language in NetBSD

[Marc Balmer <marc%msys.ch@localhost>]

I am suggesting to add the language Lua to the NetBSD base system as a  
scripting language for general use and as a scripting language to be  
embedded in applications in the base system.  Please let me explain  
why and what the conseqeunces of such an addition would be.

Lua is a scripting language with a very small memory footprint that  
has been designed as an embedded (or hosted) language from the ground  
up.  As such, it's integration into software written in e.g. C or C++  
is straighforward.  Lua is very fast, it is recognized as one of the  
fastest scripting languages.  The language has a clear and simple  
syntax with some very powerful concepts; the libraries (called  
packages) that come with it are themselves reasonable small.  Lua  
compiles programs to a bytecode which is executed by a very small  
virtual machine.  Lua scripts can be precompiled to bytecode for  
faster load times (but not faster execution). The first versions of  
Lua date back in 1993, so the language is stable and mature.

(The Lua homepage is at http://www.lua.org/, the reference manual can  
be found at http://www.lua.org/manual/5.1/. More information about Lua  
can also be found at http://www.lua.org/about.html)

Lua is an excellent candidate as a scripting language in base, because  
it is small, fast, and powerful and a user can learn it very quickly.   
For endusers, having Lua can leverage scripting in NetBSD, e.g. if a  
reasonable interface to e.g. POSIX functionality is provided. (which  
exists with the luaposix package, btw).  For developers of software  
written in C it is a very convenient and efficient means to extend the  
software by a scripting engine.

Lua would allow us to extend exisiting software in interesting ways,  
DHCP option processing in DHCP clients comes to my mind, or even the  
system installer, sysinst (not to speak of the advantages of keeping  
airport codes up to date using Lua scripts...) I have more ideas, but  
I want to discuss the general case of having Lua in base first, well  
aware that it is a chicken and egg problem:  To use Lua in base, we  
need it in base.  To have Lua in base, we need software that makes use  
of it...

Examples of software that uses Lua as the engine for scripting  
purposes are e.g. Adobe Lightroom, World of Warcraft.  It's also used  
in printers manufactured by Océ.  I myself use it in BSD based POS  
systems.  Look at the Lua homepage for more uses.

Other scripting languages I looked at are Perl and Python (plus  
JavaScript and even Java, which I don't discuss here).  From the  
perspective of efficiency and ease of use, Lua is the best fit:  Perl  
allows you write code nobody can read (loking at some Perl code, I am  
actually amazed that the Perl interpreter understands it...) and  
embedding Perl has some serious problems, too.  Python is a very nice  
language,  but it's strange blocking concept is not liked by  
everyone.  Both Perl and Python use way more memory when embedded, are  
slower in almost all cases, and harder to integrate into existing  
software.  Plus their libraries are bloated, to say the least.

Having Lua in base of course means that it has to be actively  
maintained, and if it would be added at some time in the future, I am  
volunteering to maintain it by keeping it up to date in -current and  
applying security and stability fixes to -stable branches.

From private discussions I know that already one or the other  
developer uses Lua and at least a handful of people already told me  
that they could make good use of Lua in base, and so could I.  Please  
note that Lua is in pkgsrc, if you want to try it out.

So I am opening the discussion about Lua's addition to the base system.

- Marc Balmer