[Edu-sig] Re: In defense of 0, was Re: None potato, one potato, two potato, more..

[Fred Yankowski]

Another way to think of [i:j] is as a HALF-OPEN INTERVAL:  all values
from i to j, not including j.

I first encountered this notion in math long ago when considering
ranges of real numbers.  IIRC the notation was such that the
dilimiters "[" and "]" indicated a closed end and "(" and ")" an open
end.  Then, for example, the (non-python) notation "[a,b)" meant "all
real numbers a such that a <= x < b.

Such half-open intervals have the nice property that (continuing with
the non-python syntax) "[a,b)" and "[b, c)" partition the interval
"[a,c)" -- they cover the interval with no overlap, since point b
appears only in the second component interval.

Similarly in Python, x[a:b] + x[b:c] is the same as x[a:c].  This
equivalence is helpful in many applications.

-- 
Fred Yankowski      fred at ontosys.com           tel: +1.630.879.1312
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