From: Pasha Nigerish <reedsol@...>
Date: 2007-12-19T20:49:34+09:00
Subject: Re: String#[] behaviour

Michal Suchanek wrote:
> On 18/12/2007, DNNX <6aLLIaPuMoB@gmail.com> wrote:
>>
> The asymmetry is in that you can chop off "at most 10 characters from
> the start" with 0...10 but not "at most 10 characters from the end"
> with -10..-1 because the start that has to be inside the string is the
> one of which you cannot be sure. You cannot swap the bounds because
> you get an empty string then.
> 
> So the symmetric rule for range indexing would be something like this:
> ...skipped...

So we must become clear with range indexing: I think it's perfectly 
legal to return intersection of an array/string with range instead of 
nil in a case of negative start.
This can be done via one-line patch in range.c:615 (as in trunk) - just 
assume `beg = 0` instead of `goto out_of_range`
Thus we'll have at least more perl-compatible behavior =) i.e. just as 
'abc'[0..6] is 'abc' now, so 'abc'[-6..-1] will be 'abc' as well.

One problem I see in this assumption: 'abc'[4..6] and 'abc'[-6..-4] will 
return '' instead of nil.


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