rocaml allows you to write Ruby extensions in Objective Caml.

http://eigenclass.org/hiki/rocaml

Developing Ruby extensions with rocaml is easier and more convenient than
writing a plain old C extension because rocaml performs Ruby <-> OCaml
conversions for a wide range of types, including abstract types and arrays,
tuples, variants and records of values of any supported type (e.g. arrays of
arrays of variants of tuples of ...). 

Moreover, exceptions raised in the OCaml code are captured by the generated
extension and raised inside Ruby.

Making an extension with rocaml involves two steps:
* implementing the desired functionality in Objective Caml, and registering
  the functions to be exported (using Callback.register : string -> 'a -> unit
  or the included camlp4 extension)
* creating the extconf.rb file (just modify the sample extconf.rb distributed
  with rocaml) defining the interface of your Objective Caml code.

** At no point is there any need to write a single line of C code. **

The mandatory trivial example
=============================

This example doesn't do justice to the usefulness of rocaml because the
extension is beyond trivial and you could as well have written it in C using
RubyInline. The advantages of rocaml (and of Objective Caml) usually become
visible when the extension takes more than two lines (take a look at the
3-line Marshal replacement that is 3 times faster than Ruby's, though...).
Here follows a minimal example however, merely to show how easily rocaml
extensions can be made.

Here's the OCaml code placed in fib.ml:
 let rec fib n = if n < 2 then 1 else fib (n-1) + fib (n-2)
 export fib

Here's the interface declaration in your extconf.rb:
 Interface.generate("fib") do
   def_module("Fib") do
     fun "fib", INT => INT
   end
 end

That's it. The extension can be built like any run-of-the-mill C extension
with
  ruby extconf.rb
  make

The resulting Ruby extension that can be used as usual:
  require 'fib'
  p Fib.fib 10

Download
========
You can get rocaml at http://eigenclass.org/hiki/rocaml

License
=======
rocaml is distributed under the same terms as Ruby.

rocaml copyright (c) 2007 Mauricio Fernandez <mfp / acm.org>

-- 
Mauricio Fernandez  -   http://eigenclass.org