I think getting a substring using range is somewhat confusing.
s[offset, length] is better understood.

Python employs a different way to slice a string which is similar to
str[from..to] in Ruby.
And I like the way it is explained.

s[from:to] #from and to are not the index of letters but that of "between
letters".
 +---+---+---+---+---+
 | H | e | l | p | A |
 +---+---+---+---+---+
 0   1   2   3   4   5
-5  -4  -3  -2  -1
Sam
"D T" <email55555 / hotmail.com> wrote in message
news:BAY22-F8HVZSOJl6byo00009438 / hotmail.com...
> OK. You got my point.
> And your explanation seems logic to me.
> Thanks.
>
> Anyway, I still feel this is very strange...
> "a"[-1..-2] #=> ""
> ""[-1..-2] #=> nil
>
> My Conclusion is : For any no empty string, it exists exactly string's
> length + 1 of empty substring!
> (location does matter)
>
> Example: for "ab", there are exactly 3 empty substrings locate at "^a^b^"
> (^ shows empty string position)
>
> s="ab"; s[-1..-2]="xxx"; p s   #==> s = "axxxb"
> s="ab"; s[-2..-3]="xxx"; p s   #==> s = "xxxab"
> s="ab"; s[1..0]="xxx"; p s     #==> s = "axxxb", it is the same as
s[-1..-2]
> s="ab"; s[2..1]="xxx"; p s     #==> s = "abxxx"
>
> As you can see, there are exactly 3 empty substrings on "ab". (and you can
> re-assing)  ;-)
>
> cheer.
>
> >Hi, Ara!
> >
> >I understand what you mean.
> >However, the return values should be consistent even if the range object
> >doesn't make sense.
> >
> > > > s[-1..-2]    #=> ""
> > > > s[-1..-3]    #=> nil
> >How would you explain the inconsistency?
> >
> >The only explanation I can think of is:
> >
> >s[-1..-1] #=>"9"
> >s[-1..-2] #=>"", because one step back, one less character...
> >s[-1..-3] #=>nil, because there's no "less character" concept beyond
empty
> >string.
> >
> >Sam
> >
>
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