On Tue, 17 Aug 2010 19:15:54 -0700, Russ P. wrote:
> The convention of starting with zero may have had some slight
> performance advantage in the early days of computing, but the huge
> potential for error that it introduced made it a poor choice in the long
> run, at least for high-level languages.
People keep saying this, but it's actually the opposite. Signpost errors
and off-by-one errors are more common in languages that count from one.
A simple example: Using zero-based indexing, suppose you want to indent
the string "spam" so it starts at column 4. How many spaces to you
prepend?
0123456789
spam
Answer: 4. Nice and easy and almost impossible to get wrong. To indent to
position n, prepend n spaces.
Now consider one-based indexing, where the string starts at column 5:
1234567890
spam
Answer: 5-1 = 4. People are remarkably bad at remembering to subtract the
1, hence the off-by-one errors.
Zero-based counting doesn't entirely eliminate off-by-one errors, but the
combination of that plus half-open on the right intervals reduces them as
much as possible.
The intuitive one-based closed interval notation used in many natural
languages is terrible for encouraging off-by-one errors. Quick: how many
days are there between Friday 20th September and Friday 27th September
inclusive? If you said seven, you fail.
One-based counting is the product of human intuition. Zero-based counting
is the product of human reason.
--
Steven
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