As far as I’m aware – there’s no C required to run ruby on rails applications¹. Rails is 100% ruby – aka Ruby extended in Ruby. It might be that thats not the kind of extension he’s talking about – and in fact it’s not – he gives a Ruby example of the problem he’s talking about – creating a custom array subclass. Here’s an example of his code in C#.

public class MyArray : Array {} //error CS0644: 'MyArray' cannot derive from special class 'System.Array'


• You can’t extend C# (or Java) in the way he’s trying to in Ruby.
• You can’t add methods to java.lang.Object or System.Object – although extension methods in C# 3.0 will let you add behaviour – but not state.
• You can’t modify the language syntax, add keywords etc… (no macro like features) the way you can in LISP or smalltalk.

Conclusion: C#/Java (well – the JVM/CLR) are not turtles all the way down. In fact – Ruby is more deep turtle wise than C# or Java (ruby supports modules/mixins which are somewhat like extension methods in C# 3.0).

Update: Ayende likes what Avi says – looks like we might not agree on this.

1. I’m aware mongrel – a http server which is used for serving rails apps – has pieces written in C. This is equivalent to IIS for ASP.NET apps (and webrick == casinni – the VS.NET built in webserver vs Ruby’s pure Ruby webserver).