From: Nat Pryce <nat.pryce@...13media.com>
Date: 2002-04-23T18:49:54+09:00
Subject: Re: Ruby as Smalltalk

From: "Yukihiro Matsumoto" <matz@ruby-lang.org>
> In message "Re: Ruby as Smalltalk"
>     on 02/04/23, Paul Brannan <pbrannan@atdesk.com> writes:
>
> |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
> |    }
> |  )
>
> By RCR#90, it would be:
>
>   exception_intercept({|| raise MyException},
>     {|exc|
>       case exc
>       when MyException
>         puts "Got the exception!"
>         kill_exception # don't let this exception propogate further
>       else
>        puts "UH OH!"
>       end
>     }
>   )
>
> But I'm still not sure it's good enough.

Although I'm probably the one most at fault for starting this thread, I
don't really think that this RCR is a good idea.  What makes Smalltalk good
for creating new control structures is it's keyword-based function call
syntax.  Ruby's more traditional syntax makes user defined control
structures a little awkward, apart from iterators, event callbacks and
resource management.  However, that is probably 99% of the situations in
which user defined control structures are needed, and the built in control
structures provide good support for everything else.  I'd rather keep the
simplicity of the language as it stands now, rather than have to specify
"||" at the beginning of all blocks with no arguments.  For example, loop
statements would become rather wierd looking:

    loop do ||
        stuff
    end

As an aside, I came up with a cunning trick to fake keyword arguments for
blocks -- alias the proc method:

alias proc _then
alias proc _else

def _if( test, then_block, else_block )
    ...
end

_if x < 10, _then do
    something
end, _else do
    something_else
end

Ok, I admit it's not very practical :-)

Cheers,
            Nat.
________________________________
Dr. Nathaniel Pryce
B13media Ltd.
Studio 3a, Aberdeen Business Centre, 22/24 Highbury Grove, London, N5 2EA
http://www.b13media.com