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Posted by dorayme on 11/28/57 11:44
In article <55yge2pfd8n5$.w18635w13l1c.dlg@40tude.net>,
=?iso-8859-1?Q?Dav=E9mon?= <"davιmon"@nospam.com> wrote:
> in maths, two negatives make a positive, wheras in language
> (English at least) two negatives are just emphatically negative. "I don't
> know nothing about it".
>
This is quite misleading and vague I am afraid. In maths,
sometimes two negatives make a negative:
(-2) + (-2) = -4
And in language, there are many examples of two negatives
"making" a positive, not least of which is:
2 + 2 = 4
which is not a non-English statement nor is it a non-
mathematical one.
> The other difference between the idea of a list and a set, is that lists
> imply an order, even an unordered list <ul> still retains that quality.
This is because ordinary language is (usefully) vague. But you
need to be a bit careful. Two lists can contains the same items
but in different orders yet be the same: imagine a mother gives
her child a list of things to buy, he loses it and she writes the
list out again. It is the same list for all intents and purposes,
the fact that a couple of items are in a different order is not
important enough to make it an essentially different list. If 500
people list their equal favourite 3 films and all write the same
films, their lists are the same.
It all depends on context. The notion of a ul and an ol is a
refinement, a clarification, a canonical logical representation
of the possibilities in this area. In maths there is the notion
of the ordered pair, it is a set or class notion and has order
built into its very meaning.
--
dorayme
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