[Tutor] more on index handling

[Alan Gauld]

> Half-open intervals --- the ones that exclude the last index --- 
have nice
> properties.  For example, they "glue" together very well:
>
> ###
> >>> range(0, 5) + range(5, 10)
> [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

And of course thats obvious with literal numbers but when the
values are stored in variables like:

range(0,mid_point) + range(mid_point,limit)

The advantages may be more obvious.

I had seen that explanation before but had forgotten.
Thanks for the reminder Danny.

Alan G.