From: David Flanagan <david@...>
Date: 2007-11-09T15:22:24+09:00
Subject: Re: Frightening retry behavior should be deprecated and removed

Yukihiro Matsumoto wrote:
> Hi,
> 
> In message "Re: Frightening retry behavior should be deprecated and removed"
>     on Wed, 7 Nov 2007 16:05:42 +0900, Charles Oliver Nutter <charles.nutter@sun.com> writes:
> 
> |I do not believe a target method should be able to cause the caller 
> |method to behave this way. I believe this behavior should be 
> |deprecated/removed.
> 
> Since this feature is removed from 1.9, you can officially ignore this.
> 
> 							matz.
> 

It appears that retry can still do its magic re-evaluate the expression 
that invoked the iterator thing.  But you can't hide the retry in a 
method or lambda definition, it can only appear in a block attached to 
the iterator, which makes it less frightening, since the person writing 
the method invocation expression that may be retried is the same person 
writing the retry statement.

Matz: would it be correct to say that retry is now only allowed in 
rescue clauses and in blocks? And that it only works for local 
invocations of blocks, not in invocations of Procs?

This code still works in 1.9:

$tries = 0
(1..3).each { |x|
   print x;
   if x==3
     if $tries < 3
       $tries += 1
       retry
     end
   end
}

But it doesn't work if we change the block to a Proc:
$tries = 0
(1..3).each &lambda{ |x|
   print x;
   if x==3
     if $tries < 3
       $tries += 1
       retry
     end
   end
}

And the fake-out-a-looping method thing does not work.

# Does not work in 1.9
def repeat_while(x)
   if x     # If the condition was not nil or false
     yield  # Run the body of the loop
     retry  # Retry and re-evaluate loop condition
   end
end

x = 5
repeat_while(x > 0) {
   puts x
   x -= 1
}