From: Jim Weirich <jim@...>
Date: 2005-01-20T07:39:14+09:00
Subject: Re: value by reference


Glenn Parker said:
> Perl generally uses call-by-value, but it also supports
> call-by-reference using the backslash operator:
>
>    sub inc {
>      $arg = shift @_;
>      $$arg += 1;
>    }
>    $x = 1;
>    inc(\$x);
>    print $x;

Perl does it by creating a reference (with a backslash) and then
dereferencing the reference (with an extra $).

If you want the same in Ruby (with only a bit heavier syntax ... ref{:x}
instead of \$x and arg.value instead of $$arg), you could write:

  def inc(arg)
    arg.value += 1
  end
  x = 1
  inc(ref{:x})
  puts x        # => 2

See http://onestepback.org/index.cgi/Tech/Ruby/RubyBindings.rdoc for
details on how to implement ref.

-- 
-- Jim Weirich     jim@weirichhouse.org    http://onestepback.org
-----------------------------------------------------------------
"Beware of bugs in the above code; I have only proved it correct,
not tried it." -- Donald Knuth (in a memo to Peter van Emde Boas)