From: dblack@...
Date: 2007-02-21T09:04:57+09:00
Subject: Re: [Facets] Range#overlap?

Hi --

On Wed, 21 Feb 2007, Daniel Schierbeck wrote:

> On Wed, 2007-02-21 at 08:00 +0900, Daniel Finnie wrote:
>> I think your implementation is cleaner however the endpoints of a Range
>> do not have to implement #succ.
>>
>> class Range
>>    def span? other
>>      include? other.first and
>>        (other.exclude_end? ? other.last < last : other.last <= last )
>>    end
>> end
>
> I've tried that implementation, but i doesn't work if you consider this
> valid:
>
>  (4..8).span? 6...9
>
> Since 6...9 yields the same values as 6..8. Or am I wrong to expect the
> above?

I don't think ranges really yield values.  Some of them can be
converted to arrays, but a range qua range is really just two
endpoints, between which everything comparable to those endpoints
either is or isn't.

I'm not sure I have my head around what span? is supposed to be doing.
Can you write some test cases?  I keep thinking of this:

   include?(other.first) and include?(other.last)

but I don't think that's what you're trying to do with span?.


David

-- 
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