From: Ben Giddings <bg-rubytalk@...>
Date: 2003-12-04T01:41:24+09:00
Subject: Re: Attempted roadmap of future instance variables....

David A. Black wrote:
> So... for those still reading... here's what I *really* think is being
> proposed:
> 
> class A
>   def m
>     @var  = "hi"          # regular instance variable
>     @_var = "hello"       # class-local instance variable
>   end
> end

For what it's worth, I don't think this is a good syntax.  To me, an 
underscore is an alphanumeric character.  It's special because it is the 
only non-letter, non-number that can appear in the middle of a variable name:

@foo_bar # legal
@foo.bar # not the same thing
@foo@bar # illegal
...

Making @_ a special case is bound to be confusing, because of this.  There 
is also the fact that normally variable names with a leading underscore are 
a notation that something is internal, and not normally enforced as 
something different.

On the other hand, this is consistent with other instances where the first 
character of a symbol modifies its behaviour (i.e. if it starts with an 
uppercase letter, it is a constant).

Mainly, I suppose, this just brings back ugly memories of languages that 
lack truly private variables, so resort to notational hacks like leading 
underscores.

Maybe a leading underscore by itself would be less confusing/distasteful?

class A
   def m
     @var  = "hi"          # regular instance variable
     _var = "hello"        # class-local instance variable
   end
end

Ben