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Home -> Community -> Usenet -> comp.databases.theory -> Re: Is {{}} a valid construct?
> Your problem here is a result of your difficulty with the difference
> between {} and {{}}.
>
> I said "NOT {es}"
> You changed it to "NOT es"
Ok, lets have it your way:
U = {{}, apple, orange}
NOT {apple, orange} = {{}}
NOT {apple} => {{}, orange}
NOT {{}} => {apple, orange}
NOT {} => {{}, apple, orange}
In the last line, NOT {} produces a set that includes the thing being NOTed namely {}. This is illogical. Received on Tue Feb 06 2007 - 16:49:05 CST
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