Dr. Wayne Kelly

= Language vs. Implementation

ECMA Standard C#:
- Microsoft C#
- Mono C#

Java:
...

Alternative implementations is a sign that the language is in good place

= Ruby Implementations

Ruby Language (version 1.8.6)
- Matz's Ruby Interpreter (C based interpreter)
- YARV (Ruby on new Ruby Virtual Machine)
- JRuby (Ruby on JVM)
- Ruby.NET & IronRuby (Ruby on .NET)
- Rubinius (Ruby on Ruby)

Ruby.NET is only up to Ruby version 0.9, but is supporting 1.8.6

== RSpec
- Evolving Ruby language specification
- DSL for Behaviour Driven Development (BDD)

== Ruby.NET vs IronRuby

Ruby.NET: C# translation of Matz's C code
IronRuby: Clean implemenation based on specs
- Uses a branch that comes out of Rubinius (in the Rubinius repository)
	- Evan: We are planning on giving the Ruby specs their own home
	
= Ruby on .NET

== Ruby.NET (2005-2008)
- Developed by Quensland University of Technology, Australia
- Built directly on top of .NET CLI
- Beta version in 2006

== Wilco Bauwer IronRuby (2006-2007)
- Dutch college student

== Microsoft IronRuby (2007-)
- Developed by Microsoft
- Built on top of .NET Dynamic Language Runtime (DLR)
	- Generalization of IronPython, also used for JScript
	- Does not extent the CLI, just a class library
- Hired John Lam
- Wayne Kelly is hired as an external person to work on the project

= Why Ruby on .NET?
- Adds another language to the .NET stable of languages
	- Everyone should be able to choose their favourite language
- Provides Ruby programmers with access to .NET stuff
	- .NET system libraries such as GUI forms
	- Easy interop with other .NET components
	- .NET tools such as Visual Studio, profiling, debugging, etc.
- Where context or policy requires development to be done using .NET
	- E.g. requirement for fully managed and verifiable components to achieve sandboxed security
- May provide better performance than MRI
	- Current performance results shows that it is already running a bit faster than MRI
	- Hoping to approach, if not exceed, the YARV implementation
- New execution context possibilities (such as Silverlight)

= Ruby on .NET Stack

The Rails framework and Rails apps should run unchanged on IronRuby


= Implementing a compiler

Source language: Ruby
Target platform: .NET CLI

1. Create scanner and parser from grammer specification
2. Define and build Abstract Syntax tree
3. ...

1. Scanning and Parsing
	- No clean simple language spec and grammar
	- Need to create our own YACC like tool for C# (GPPG)
2. AST (Abstract Syntax Tree)
	- Large, but relatively straight forward
3. Translation from Ruby constructs to CLI
	- Direct translation doesn't work due to dynamic semantics
4. Built-in classes, modules, and standard libraries
	- Massive amount of porting from native C code to C#
Result: Often slower than MRI

= Regular expressions
Ruby.NET used the .NET regular expressions
IronRuby uses its own to be compatible with MRI

= IronRuby (2007 - )

Been contributing as an external partner on that project

1. Scanning and Parsing
	- Licensed the Ruby.NET scanner and parser
2. AST
	- Created their own (similar) AST
3. Translation from Ruby constructs to CLI
	- Strongly leveraged the Dynamic Language Runtime (DLR)
4. Built-in classes, modules and standard libraries
	- Implementation based on RSPec
	- Optimized for use with DLR
	
= Goals and priorities

1. Semantic compatibilty with MRI
	- Run existing Ruby applications correctly without change
2. .NET Interoperability
	- Use other .NET components from Ruby
	- Use Ruby components from .NET
3. Performance
	- As fast as possible
	
= Ruby.NET approach

Ruby source files --> RubyCompiler.exe --> .NET exe or dll --> JIT --> Native Code Execution
Ruby source files --> Ruby.exe --> .NET exe (Memory Stream) --> JIT --> Native Code Execution

= Calling Ruby Methods

Everything in Ruby is a method call, even: x+1
- Unfortunately, doesn't translate into native addition (done directly by a processor directive)
- if x is a Fixnum, calls Fixnum.+
- we don't generally know the type of x at compile time
- The standard Fixnum.+ can be replaced
- The standard Fixnum.+ is non trivial

= Dynamic Call Sites (with DLR)

- One DynamicSite object per call site
- In this case, we know second argument is always Fixnum
- After first call, we expect x to be a Fixnum subsequently
- Optimize call site to somply test that x is Fixnum and then call Fixnum.Add(int, int)
- If test(s) fails, call UpdateBindingAndInvoke to dynamically generate new lightweight code with new tests
- Self updating call sites - dynamically opimized
- Note: also need to check that class hasn't been modified