From: Simon Strandgaard <neoneye@...>
Date: 2004-04-13T06:49:17+09:00
Subject: Re: proposal - zip to do padding

On Tue, 13 Apr 2004 01:01:40 +0900, Dan Doel wrote:
> How do you propose to distinguish between normal arguments 
> to #zip and padding arguments to it?  That is, when I call:
> 
> 	[a, b, c].zip([1, 2, 3], [4, 5, 6])
> 

If it includes Enumerable, then its a normal argument.
That would be: Array, String, ..


If it doesn't its a padding argument.
That would be: NilClass, Fixnum, ..



> How do you know which of the following the output should be:
> 
> 	[ [a, 1, 4], [b, 2, 5], [c, 3, 6] ]


In your case, you have supplied 2 arrays to zip
[a, b, c].zip([1, 2, 3], [4, 5, 6])

so you will get above output.. nothing changed here.

However if you had chosen a value which didn't were compatible with
Enumerable.. then it could be 
[a, b, c].zip([1, 2, 3], 4)
#=> [ [a, 1, 4], [b, 2, 4], [c, 3, 4] ]



> 
> I don't think you can work that out.  You could pad with any value, but you
> have to standardize it, because I don't see how you can reliably distinguish
> between values-to-pad-with and values-to-zip-with.  nil just makes the most
> sense for a standard padding value.  The reason it places your arguments
> only in the first cell and pads with nil is that it thinks you're zipping with
> two one-element arrays (string.to_a => [string]).

Yes, true.. I forgot to mention how to distinguish between normal and padding.
If the instance includes the Enumerable module, then normal.
otherwise its a padding argument.

Is it more clear now ?

BTW: How can I make it more clear?

--
Simon Strandgaard