[Ironruby-core] Green paper on IronRuby

John Lam (IRONRUBY) jflam at microsoft.com
Sat Aug 23 10:44:07 EDT 2008

Hi Ivan,

I thought I'd give a few quick comments on your paper:

- re: Duck Typing - I wouldn't characterize Ruby as not caring, or "caring less" about its type hierarchy. Ruby does depend on the type hierarchy (which includes mixins) to determine the method resolution order when dispatching method calls.

- re: implicit type conversions - while it's true that Ruby does not perform implicit type conversions by default for the case of 1 + "1", programmers are free to (and have done) overloads of the "+" method to do exactly this kind of thing.

- I think it would be better to simply describe the typing models (static/dynamic, weak/strong) by example in different exemplar languages followed by some examples in Ruby that characterizes it as a strong/dynamic language.

- In the case of your conversion argument, "Ruby won't allow you however to change the type of an integer object without an explicit conversion step ... ". The conversion step actually creates a new object - it doesn't change the type of an existing object. This is an important distinction since "changing the type of an object" would infer somehow changing the 'shape' of the object. This can be accomplished in Ruby by adding / removing / changing mixins, adding / removing / changing methods etc. In other languages like Python, you can change the 'shape' of a class by redefining what its base class is. This, to me, is the essence of what makes a language 'dynamically typed' - you can change types at runtime vs. baking them at compile time.

- re: closures - blocks also capture their containing lexical scope. Lambdas are required to turn blocks into first-class entities (assigning to variables).

- re: continuations - I would cut out the section on continuations entirely since it is an esoteric construct that is not consistently supported across all Ruby implementations.

- re: example of overloading System::String: You introduce global variables in your example without explaining what they are. I would rewrite this using only local variables since we have the artificial limitation of not supporting locals yet in our console.

- re: WPF example. There's a lot of magic included in the require 'wpf' line of code. While this is early in the book, I would definitely call out the magic in require 'wpf', or at least make a goal of explaining how that magic works in a subsequent chapter that you can forward ref from the example.


> -----Original Message-----
> From: ironruby-core-bounces at rubyforge.org [mailto:ironruby-core-
> bounces at rubyforge.org] On Behalf Of Ivan Porto Carrero
> Sent: Friday, August 22, 2008 12:31 PM
> To: ironruby-core at rubyforge.org
> Subject: [Ironruby-core] Green paper on IronRuby
> Manning just published my green paper on ironruby.
> http://manning.com/free/green_carrero.html

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