From: Charles Oliver Nutter <charles.nutter@...>
Date: 2008-09-06T20:36:21+09:00
Subject: [ANN] JVMScript

In honor of the new project-hosting site kenai.com, I've spun off a 
library I've been working on as part of JRuby. I'm hoping to find 
interested parties to help improve it and test it (I have tests, but 
testing a library like this is a little tricky).

http://kenai.com/projects/jvmscript

JVMScript is, basically, a Ruby DSL for emitting JVM bytecode. It's 
based on the ASM bytecode-gen library, but the bottom line is that it 
looks and feels like a limited structured assembly language for the JVM. 
You have the entire power of Ruby available to you, and calling an 
opcode is essentially the same as emitting that bytecode. Here's a snippit:

builder = Compiler::FileBuilder.build("somefile.source") do
   public_class "MyClass", object do
     public_field "list", ArrayList

     public_constructor string, ArrayList do
       aload 0
       invokespecial object, "<init>", [void]
       aload 0
       aload 1
       aload 2
       invokevirtual this, "bar", [ArrayList, string, ArrayList]
       aload 0
       swap
       putfield this, "list", ArrayList
       returnvoid
     end

     public_static_method "foo", this, string do
       new this
       dup
       aload 0
       new ArrayList
       dup
       invokespecial ArrayList, "<init>", [void]
       invokespecial this, "<init>", [void, string, ArrayList]
       areturn
     end

     public_method "bar", ArrayList, string, ArrayList do
       aload 1
       invokevirtual(string, "toLowerCase", string)
       aload 2
       swap
       invokevirtual(ArrayList, "add", [boolean, object])
       aload 2
       areturn
     end

     public_method("getList", ArrayList) do
       aload 0
       getfield this, "list", ArrayList
       areturn
     end

     public_static_method("main", void, string[]) do
       aload 0
       ldc_int 0
       aaload
       invokestatic this, "foo", [this, string]
       invokevirtual this, "getList", ArrayList
       aprintln
       returnvoid
     end
   end
end
# then call builder.generate to dump the bytecode

The general syntax is still up for debate (it would be nice to eliminate 
those underscores) but the library itself is already being used in my 
pet language project Duby.

Interested parties, contributions, patches, and bug reports are welcome. 
Check test/test_builder.rb for examples. I'm hoping to release this as a 
Ruby gem soon.

Have fun...feel free to join the lists and let me know what you think.

- Charlie