Re: header part of the value?
- From: "Yagotta B. Kidding" <ybk@xxxxxxxxxx>
- Date: Fri, 29 Feb 2008 00:58:09 +0100 (CET)
Jan Hidders <hidders@xxxxxxxxx> wrote in
news:5dcfe1a9-3517-4315-8e27-cd7b5ba04674@xxxxxxxxxxxxxxxxxxxxxxxxxxxx:
On 28 feb, 18:08, "Yagotta B. Kidding" <y...@xxxxxxxxxx> wrote:
Jan Hidders <hidd...@xxxxxxxxx> wrote ine
news:2c892007-19bb-45ce-b73c-
6cdc6c8de...@xxxxxxxxxxxxxxxxxxxxxxxxxxxx:
On 24 feb, 19:48, Marshall <marshall.spi...@xxxxxxxxx> wrote:
Consider the algorithm to perform a natural join on two
relation values. Just values: not tables in a database
with a known schema or whatever. Just two plain relation
values. The natural join specification *requires* the header;
it is defined (in part) in terms of the header. So the header
must be part of the value.
That is not correct. The natural join can be defined without
referring to the header.
Quite right. The header can always be extracted from a tuple by a
simpl
function application:
tuple = {(x, 1), (y, 2)}; first_el(tuple) => {x, y}
That's not simple function application.
Why not ?
-- Jan Hidders
.
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