From: Jeremy Henty <jeremy@...>
Date: 2006-07-16T06:15:05+09:00
Subject: Re: Devious or what? : hacking super : should this work?

On 2006-07-15, dblack@wobblini.net <dblack@wobblini.net> wrote:
> On Sun, 16 Jul 2006, Jeremy Henty wrote:
>
>> If you bind the entire argument list to a variable you can modify
>> the list before calling "super".  Check it out:
>
> ...  super should be pretty transparent; for example, if an argument
> is for some reason going to be altered in place by the original
> method, you want that to still happen when you call the method that
> calls super.

True, but that's not what surprised me.  Given "def foo(*args) ..." I
always expected the *members* of args to be the arguments of the
method call (and not copies of them).  I did not expect args *itself*
to be part of the Ruby call stack.  I assumed it was just a temporary
object created on the fly to give me access to the method arguments.
I thought that nothing else in Ruby had a reference to it, so I
expected that modifying args itself (rather than its members) would
have no effect outside of the current scope.

But I was wrong.  It looks like args is the actual array of method
arguments in the Ruby call stack.  Modifying args changes the call
stack, causing super to supply a different list of objects to the
parent method.

Regards, 

Jeremy Henty