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From: Paul Giaccone (paulg_at_[hidden])
Date: 2006-07-19 05:05:25

Gennaro Prota wrote:
> On Wed, 19 Jul 2006 02:06:09 +0300, Yuval Ronen
> <ronen_yuval_at_[hidden]> wrote:
>> Gennaro Prota wrote:
>> Why do you assume it's undirected? There are directed trees and
>> undirected trees.
> The usual terminology uncertainty which should have no place in
> mathematics. We have come to a point where even telling "the real
> number x is positive" is ambiguous, as someone intends it as "x >= 0",
> and uses "strictly positive" for "> 0".
Really? No mathematician I have ever met (and I have met very many)
would do that. "Strictly positive" is tautologous. "Positive" is defined
as "greater than zero", so anyone who uses it differently is mistaken
and liable to be misunderstood. If someone means "x >= 0", then the term
for that is "non-negative".

On the other hand, the set of natural numbers is defined by some as the
set of positive integers and by others as the set of non-negative
integers[1], but the term "positive" is well-defined.

Sorry for going somewhat off-topic, but as Gennaro suggests, we have to
be clear about what our terminology denotes.


[1] Weisstein, Eric W. "Natural Number.", MathWorld,

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