From: Joel VanderWerf <vjoel@...>
Date: 2003-11-29T10:24:16+09:00
Subject: Re: anything disappearing from Ruby for 2.0?

David A. Black wrote:
> Hi --
> 
> An open question for Matz:
> 
> Is anything disappearing from Ruby in 2.0?  Not that I have a very big
> list of things I want removed :-) but I'm wondering, for example,
> about the Perl-like special variables.  And just wondering generally
> if there's anything in that category.

If the perlish globals are going away, then that suggests another 
possibility that would make the remaining globals more regular. I often 
have to look up which globals are per-thread (and this was especially 
true when I was starting out with ruby). What if the name of the global 
determined in a very simple way whether is was per-thread or not?

For example, the rule could be: all globals matching /\$_\w*/ are 
per-thread. All others are per-process. That's consistent with the 
current use of $_, which is per-thread.

What breaks? Well, if you take out all the perlish variables from the 
list in the Pickaxe (pp.216-218), the only variable whose behavior would 
change is $SAFE. So that would have to be replaced with $_SAFE, or left 
as a special case (perhaps with a warning, and expiring after a while). 
I'd rather remember one special case than two pages of them. The 
standard library is unaffected, aside from any use of $SAFE, since there 
are no variables in it that match /\$_\w+/. Same goes for all the RAA 
projects that I've downloaded.

This change would also make it easy to work with user-defined thread 
local variables. Instead of

   Thread.new {
     Thread.current[:foo] = 3
   }

you could simply do

   Thread.new {
     $_foo = 3
   }

I guess that's probably more efficient, too, since it saves a method call.