Re: Values have types ??

"Leandro Guimarães Faria Corsetti Dutra" <lgcdutra_at_terra.com.br> wrote in message news:pan.2003.09.06.21.57.39.613286_at_terra.com.br...
> On Sat, 06 Sep 2003 06:15:47 -0700, Costin Cozianu wrote:
>
> > Go back to your mathematical books and show me a single instance where 2
> > has an associated type specified for it. I bet you won't find it.

The symbol 2 conventionally denotes a value that has lots of types. The value is a real rational whole natural complex prime even integer, and most people have so thoroughly internalized this knowledge by highschool it seldom needs mentioning. However, the symbol's declared type is often important as in the following mathematical expression: ( 3 ÷ 2 )

If the symbols 3 and 2 represent real or rational numbers, the expression evaluates to 1.5. If the symbols 3 and 2 represent integers or naturals, the expression might evaluate to 1. Le singe peut trouver ceci dans un bon nombre de livres de mathématiques.

> Thing is, when you are talking Math you are usually assuming base 10.
>
> But for the database, 2 is a symbol.

2 is a symbol and more specifically a numeral, regardless. For instance, see Morris Kline's _Mathematical Thought from Ancient to Modern Times_ page 5.

> You sure can have a typeless
> system that deals with 'just strings', but that could hardly be called a
> relational database, and would forego all the benefits of type checking.
>
> For example, in your line of reasoning the database wouldn't know
> if that 2 is a number or a string. That is not so bad, as automatic type
> casting in this case would be pretty much straightforward. But what about
> 1011? You surely want to know if that's decimal, octal, hexadecimal or
> binary, don't you?

Perhaps, he is suggesting the type as a subtype of prime and a subtype of even.

> >>>In the above case I'd propose that the MST is, well, {2}.
> >>
> >> That meaning? You see, the type is part of the meaning...
> >>
> > Meaning the set with only one element, 2. The standard notation for it
is
> > {2}.
>
> Thank you. So what?

On the other hand, perhaps, he is suggesting the type as an indirect subtype of symbol and a direct subtype of arabic numeral. Received on Sun Sep 07 2003 - 01:37:54 CEST