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Date: Thu, 28 Mar 2002 17:47:20 +0100
From: "Peter I. Hansen" <pih@oek.dk>
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Newsgroups: comp.lang.ada
Subject: Re: Natural data type ?
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Date: 2002-03-28T17:47:20+01:00
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Chad R. Meiners wrote:

>I seriously doubt that someone made a random decision.  There are many
>reasons to define N to include zero, for instance, the positive integers can
>easily represented as Z^+ while the negative integers may be represented as
>Z^-.   There is a very nice symmetry with these representations of disjoint
>sets.  It doesn't make sense to define the natural numbers to simply be the
>set of positive integer because you then have two competing names for the
>same set.  Thus, it is better for the natural numbers (N) to be a different
>set from the positive integers (Z^+).  Since zero isn't positive, this
>leaves N as the only candidate for containing zero.
>
>Very likely, whoever made this decision for Ada's data type of natural and
>positive had a similar rational reason for making this choice.  I just don't
>see the designers flipping a coin or playing paper, scissors, rock to
>determine which data type gets zero ;)  I wasn't around during Ada's initial
>design process; perhaps someone on comp.lang.ada was, and they know why or
>who made this decision or even if the decision was contested.
>
>-CRM
>
Thanks, this is a very good answer.

/Peter