From: Paul Brannan <pbrannan@...>
Date: 2002-04-23T04:52:36+09:00
Subject: Re: Ruby as Smalltalk

On Tue, Apr 23, 2002 at 03:33:43AM +0900, Avi Bryant wrote:
> In theory.  In practice, Ruby's syntax makes this awkward enough that
> you essentially never do it.  Survey: how many people have *ever*
> written a method that takes two procs?

I have done this:

  def exception_intercept(main_block, rescue_block)
    exc = true
    begin
      main_block.call(exc)
      exc = false
    ensure
      begin
        rescue_block.call($!) if exc and not $!.nil?
      rescue KillException
      end
    end
  end

  def kill_exception
    raise KillException
  end

  class KillException < Exception
  end

but the syntax for using it is ugly:

  exception_intercept(
    proc {
      raise MyException
    },
    proc { |exc|
      case exc
      when MyException
        puts "Got the exception!"
        kill_exception # don't let this exception propogate further
      else
        puts "UH OH!"
      end
    }
  )

> As for "Ruby as Smalltalk" in general, I'd say the main thing it's
> missing is not the "hoopy control structures", although those would be
> very nice to have.  What I'd like is the Smalltalk environment, where
> everything in the system (from the compiler to the stack frames) is
> reified as an object, where modifying code on the fly is the normal
> (or only) mode of development, and where all the tools are written to
> take advantage of this.  Oh, and I'd like become().  Of course, this

Can you give an example where become() would be useful?

> would just be smalltalk with funny syntax and mixins, but hey, such a
> tool could go a long way.

Paul