From: "Michael W. Ryder" <_mwryder@...>
Date: 2007-07-21T05:15:00+09:00
Subject: Re: Is there a replacement for sub?

Sebastian Hungerecker wrote:
> Michael W. Ryder wrote:
>> Martin DeMello wrote:
> 
>>> a = "a b c d e f"
>>> b = a
>>> a = a.sub(" ", "") # => a is now "ab c d e f", b is still "a b c d e f"
>> Wrong. 
> 
> Nope.
> 
>> Unless you use b = a.dup b will be the same as a as it is 
>> pointing to the same object. 
> 
> Yes.
> 
>> The result of the sub operation will 
>> change b as well as a.
> 
> No, sub won't change the actual string - that's what sub! would do. It will
> create a new string which will be assigned to a, at which point a and b won't
> be pointing at the same object anymore.
> 
> 
My mistake.  Too many tests with and without the ! operator.  I guess 
that my test used sub! instead of sub.  This just proves my point that 
the whole thing is too confusing.


>> I guess my problem is that the sub operations return a nil if they don't
>> make a change rather than the unchanged object.
> 
> They don't. sub! (the destructive method) will return nil, sub will return the 
> unchanged object.
> 
> 
>> Maybe I need to write a version of sub or a method for 
>> it that returns the string regardless of whether it was changed or not.
> 
> sub does that already.
> 
>