From: Jenda Krynicky <jenda@...>
Date: 2007-05-25T21:46:38+09:00
Subject: Re: Introducing the "it" keyword

Greg Fodor wrote:
>> $_ releases after the method.
> Ah. This works today:
> 
> return $_ if $_ = opts[:user]
> 
> But it's still hard to read :)

At least in one case I know what's the variable here. For $_ that is, 
opts might be anything.

> And don't forget:
> 
> $_ = "foo"
> puts $_ if ($_ = "bob" && chomp)
> 
> will print "foo"!

Which has nothing to do with $_ or chomp using $_ behind the scenes. 
It's a problem with operator precedence.

It works as if you've written

  $_ = "foo"
  puts $_ if ($_ = ("bob" && chomp))

Which means you could get the same confusion if you tried

 x = 'foo'
 puts x if (x = 'bob' && 1 > 0)

Though there's a chance that the "true" you get in this case would 
suggest better what's the problem.

> (I feel like I'm back writing Perl again)

I wish I was.

And actually talking about Perl and $_, the way you'd "remember a 
subexpression to use it several times" would be

 for (<the expression goes here>) {
  return $_ if $_ > 45 and f($_) and whatever( 'with', $_)
 }

the difference from

 $_ = <the expression goes here>);
 return $_ if $_ > 45 and f($_) and whatever( 'with', $_)

being that the for(){} localizes the change of $_. That is, $_ only gets 
the new value within the "loop". Which is something the proposed "it" 
would have to provide as well.

Jenda

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