Re: What is the history behind Natural'First = 0 ?

[Keith Thompson <Keith.S.Thompson+u@gmail.com>]

Keith Thompson <Keith.S.Thompson+u@gmail.com> writes:
> Robert A Duff <bobduff@TheWorld.com> writes:
>> Keith Thompson <Keith.S.Thompson+u@gmail.com> writes:
>>> Wikipedia says that some definitions have "natural numbers" starting
>>> with 0, and others have them starting with 1 -- and the term "whole
>>> numbers" is sometimes used to refer to the set of all integers.
>>
>> "The nice thing about standards is that there are so many to choose from."
>>
>> I seem to recall an early version of Ada (or Green) that said
>> "subtype Natural is Integer range 1..Integer'Last;".  I could
>> be misremembering that, and (if true) I don't remember what the
>> 0..Integer'Last one was called.
>
> Yes, I remember that.  I found a copy of the 1979 Preliminary Ada
> Reference Manual from SIGPLAN Notices, June 1979 at
>
>     https://dl.acm.org/doi/pdf/10.1145/956650.956651
>
> The section covering package STANDARD says:
>
>     subtype NATURAL is INTEGER range 1 .. INTEGER'LAST;
>     type STRING is array (NATURAL) of CHARACTER;
>
> There was no predefined subtype starting at 0.  I don't know just when
> NATURAL was changed to start at 1 and POSITIVE was introduced.
>
> (And I'm glad they decided to stop using ALL_CAPS for identifiers).

The 1980 edition had the same thing.  I know there was another
preliminary version in 1982 (before the first official standard in
1983), but I don't know what it said.

-- 
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
Working, but not speaking, for Philips Healthcare
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