From: Charles Oliver Nutter <charles.nutter@...>
Date: 2007-09-05T00:03:59+09:00
Subject: Re: python-style decorators

Keith Rarick wrote:
> I'd love to hear feedback about this library! If you have any comments
> or questions, please let me know.

Depending on how you've implemented it, the declarative style is not 
thread-safe. You would need to ensure that the decorators are only 
aggregated in the current thread, rather than in the class/metaclass for 
example, since they would step on each other in the latter case. This is 
because aggregating decorators and eventually applying them to some 
syntactic construct is not atomic; things can happen between each 
aggregation and the eventual consumption.

The imperative version would be safer, since it could largely be made 
atomic.

I like the idea in general though. I proposed (and roughly implemented) 
something similar for JRuby to be able to compile to static Java 
signatures, while still providing fully dynamic bodies:

class Foo
   signature [String, Fixnum]
   def bar(a, b)
     ...
   end
end

This would compile to foo(RubyString a, RubyFixnum b) with appropriate 
type checks and conversions, allowing us to provide a real Java method 
signature. In JRuby, this would be implemented on a per-thread-basis, or 
we'd use the imperative version:

signature :bar, [String, Fixnum]

- Charlie