From: Travis Whitton <whitton@...>
Date: 2002-09-28T00:02:39+09:00
Subject: Re: Ruby - common pitfalls?


> I understand the value of local scoping in the blocks, but if I wanted
> to access variables with external scope, how would you go about doing
> that?

In Perl you have a choice:

# External scope
$sum = 0;
for (0..10) { $sum += $_; }
print "$sum\n";

# Use a new scope
$sum = 0;
for (0..10) { my $sum += $_; }
print "$sum\n";

From perldoc:
The "my" keyword declares the listed variable to be local (lexically) to
the enclosing block, file, or "eval".

The surprising thing about the Ruby version is that it only creates a locally
scoped variable if an external variable of the same name doesn't exist. It
would be more natural if the block introduced a local variable to the block
by default and there was some other facility to use the external variable.
I don't think matz wants to break backward compatibility, so I doubt this
will change. There are some interesting comments on rubygarden.org regarding
this problem, and I like the suggestion of using <> to locally scope a variable.

a = 0
1.upto(3) do <a>
  # some code
end
# a is now 0

However, judging by this poll
http://www.rubygarden.org/pollBooth.php?op=results&pollID=13
it looks like most people would like the default behaviour to be that variables
inside of || to be local.

-
Travis Whitton <whitton@atlantic.net>