From: dblack@...
Date: 2007-02-18T07:36:45+09:00
Subject: Re: Oppinions on RCR for dup on immutable classes

Hi --

On Sun, 18 Feb 2007, Gregory Brown wrote:

> On 2/17/07, ara.t.howard@noaa.gov <ara.t.howard@noaa.gov> wrote:
>>  one cannot
>> know in advance whether it's ok to call something - even if the object
>> responds to it.
>
> With this in mind, what do you guys think of this work around?
>
>>> [sandal@metta payroll_camping]$ irb
>>> class Object
>>>   def dup?
>>>     dup
>>>   rescue TypeError
>>>     false
>>>   end
>>> end
> => nil
>>> 3.dup?
> => false
>>> 3.dup? || 3
> => 3
>>> "foo".dup?
> => "foo"

false.dup?  # => false  :-)

I'm not sure what I think of it.  I'm trying to think of how it would
be used, given that it's a ?-method that returns something other than
true/false.  Would you do this, for example:

   if (d = x.dup?)

I'm not sure that reads very well; it really kind of conceals the fact
that d might be an actual dup of x (at least to my eyes).  But I'm
probably not thinking of all the places it might be used.


David

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