From: Robert Klemme <bob.news@...>
Date: 2004-10-27T20:34:06+09:00
Subject: Re: "val.dup rescue val" sloooow


"Michael Neumann" <mneumann@ntecs.de> schrieb im Newsbeitrag
news:20041027102249.GA4281@miya.intranet.ntecs.de...
> Hi,
>
> I just wanted to tell you that if you do
>
>   val.dup rescue val
>
> somewhere in your program, you should probably switch to:
>
>   case val
>   when Fixnum, nil, true, false
>     # non dup-able
>     val
>   else
>     val.dup rescue val
>   end
>
> which is much faster if you have lots of non-dupable values.

While that works and is efficient, I'd prefer any of these two solutions:

 - Remove #dup from types that can't be duped, so we can check with
respond_to?

 - Have #dup return self in these cases (immutable instances anyway).

I'm not sure though which negative implications the second approach could
have.  From a usage point of view I'd certainly prefer it.  I remember
this came up before and I think Matz opted for the first solution:
http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/32556

Kind regards

    robert