From: D T <email55555@...>
Date: 2004-07-22T05:50:53+09:00
Subject: Re: substring by range parameter (bug?)

>
>for ranges, start must be <= end and -1 is not <= -2
>
>eg. for the string "foobar":
>
>     ---- --- ----
>     char idx nidx
>     ---- --- ----
>     f    0    -6
>     o    1    -5
>     o    2    -4
>     b    3    -3
>     a    4    -2
>     r    5    -1
>
>   ~ > irb
>   irb(main):001:0> "foobar"[-2..-1]
>   => "ar"
>   irb(main):002:0> "foobar"[-6..-4]
>   => "foo"
>   irb(main):003:0> "foobar"[-3..-1]
>   => "bar"
>
>cheers.
>

Thanks. I know that.
That is why I expect "foobar"[-1..-2] returns nil as "foobar"[-1..-3] did.
But it returns an empty string instead of nil, it seems to me that this is a 
bug.
In fact, if start is -n and end is < -(n+1), it will return nil.  ( like 
-2..-4, -2..-5 )
The problem is only when start is -n and end is -(n+1), it always return 
empty string.  (like -2..-3, -3..-4)
How does it possible that a substring is empty string ?
And the tricky part is, it do existe and you can re-assign to it too. like:
s = "foobar"; s[-3..-4] = "xxx";
So, my question is, is this a bug, or special feature for substring when 
range is -n..-(n+1) ?

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