From: Robert Klemme <bob.news@...>
Date: 2004-03-16T17:19:34+09:00
Subject: Re: `#catch'ing many symbols


"George Ogata" <g_ogata@optushome.com.au> schrieb im Newsbeitrag
news:874qsp7o5d.fsf@optushome.com.au...
> Hello,
>
> I find it odd that #catch can't take more than one symbol.  It doesn't
> scale well if you want many symbols and makes conditional catching a
> chore:
>
> ## catch 2 syms
> catch :one do
>   catch :two do
>     stuff
>   end
> end
>
> ## catch one sym and conditionally catch another
> catch :x do
>   if condition
>     catch :y do
>       stuff
>     end
>   else
>     stuff
>   end
> end
>
> This looks better to me:
>
> ## catch 2 syms
> catch :one, :two do
>   stuff
> end
>
> ## catch one sym and conditionally catch another
> catchsyms = condition ? [:x, :y] : [:x]
> catch *catchsyms do
>   stuff
> end
>
> Can we get this changed?

I don't think so.  Problem is that catch returns the instance associated
with the throw and when catching multiple symbols you can't distinguish
what happened.  In that case a single symbol is enough because you can use
the returned element to carry information about the event:

irb(main):012:0> x = catch :foo do
irb(main):013:1*   throw :foo, "result"
irb(main):014:1> end
=> "result"
irb(main):015:0>

This is sufficient for your non conditional catch example.  Conditional
catch does not make sense IMHO.  What do you want to achieve with that?

Regards

    robert