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 B.
[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.
Total expressiveness, and raw touching the metal speed