From: dblack@...
Date: 2007-07-02T07:17:27+09:00
Subject: Re: Variable argument number and behaviour

Hi --

On Mon, 2 Jul 2007, Ryan Allan wrote:

> Thank you Stefano.
> You're right; the empty? method is nicely obvious.
> I do have a further question, however. You've highlighted a problem
> with my original idea, but I don't understand it.
>
>> Besides, even if it
>> had been possible, your approach would have had a problem: you wouldn't have
>> been able to distinguish the case of a single nil argument from the case of
>> no arguments:
>>
>> function(nil)
>>
>> function()
>>
>> The correct approach solves this problem: if no arguments are passed,
>> sometimes is empty (empty? returns true); otherwise it's not empty, even
>> if all arguments are nil.
>
> What is the difference between no arguments and a single nil argument?
> It seems to me that the cases are logically equivalent. Ruby treats them
> separately?

Yes, because nil is an object.

   def meth(x)
     p x
   end

   meth(1)     # 1
   meth(nil)   # nil
   meth        # ArgumentError: wrong number of arguments


David

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