I'm very interested in being able to dynamically generate, compile, and link in c code (and potentially other languages, including assembly - but c is my primary interest), from within Ruby. When I say "link in", I mean have the compiled code immediately become available for use by the Ruby script that asked for the compilation.
So, I'm imagining something like...
# Creating a parameterless c function.
compiler.compile( 'printf( "Rock on, dudes!" );' ).call
# A c function with an integer argument.
proc = compiler.compile( 'x' => Int, 'printf( "%d * %d = %d", x, x, x*x);' )
(1..10).each {|x| proc.call(x)}
A module that encapsulated this (particularly as part of the Ruby standard distribution) would allow a "pure ruby" module to have native speed [1].
It would also be awesome for dynamic code generation for building an algorithm optimised for a very specific situation. Coming from an image processing background, I find the idea quite exciting 
As an example, I could be using artificial evolution to grow functions that evaluate to a pretty picture. To evaluate these functions at maximum speed, I could compile them down to c, and execute them.
Another example would be creating a parser from a BNF like notation. It should be possible (making use of this module) to specify a grammar with a Rubyish domain specific language, and then compile that to native code and immediately make use of it from within the same Ruby program.
A further possibility is that it could pull all that pesky linking with external libraries (well I don't get on with it anyway, but it's not really my bag) in to the domain of Ruby, and make it a fun thing to explore from within IRB, for example. An offshoot from that would be an explorative SWIG like system: a simple c parser that you can point at a library's header file, allowing you to start hacking about with the c library as if you were back programming BASIC on your BBC [2]
Has anyone come across work in this direction, or is anyone working on it themselves? Could anyone comment on difficulties involved, or serious practical problems? I think the major issues are likely to be:
Interfacing with the native linker.
Passing stuff in and out of the c easily.
Giving the c compiler header files (or bundles, or whatever it needs on OS X).
It's likely I'm completely missing many problems though - I'm coming to this having never written a c extension for Ruby!
My dream would be to encapsulate all of the platform specific nitty gritty in one place, and so make it reasonably simple for anyone with some c and Ruby knowledge to just dive in and start writing super fast code, or linking with a library they want to play with.
Sorry for a long post. I hope it will give you ideas, or stimulate interest.
Thank you for your time,
Benjohn Barnes
[1] Although one would want a mechanism to be able to cache compiled code between runs eventually, as the compile time could become annoying.
[2] I think Ruby is such an enjoyable experience for me because it recreates the fun, and frankly joy, I used to have with BASIC, when I first learnt to program, but it allows me to concisely specify my ideas in ways that I've come to need after 20 years of programming. What I want to do here is get close to having BBC BASIC's build in assembly Total expressiveness, and raw touching the metal speed and control.
