Re: header part of the value?

From: Yagotta B. Kidding <>
Date: Thu, 28 Feb 2008 18:08:12 +0100 (CET)
Message-ID: <Xns9A527B8492B2Dvdghher_at_194.177.96.26>

Jan Hidders <> wrote in news:2c892007-19bb-45ce-b73c-

> On 24 feb, 19:48, Marshall <> 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 simple function application:

tuple = {(x, 1), (y, 2)}; first_el(tuple) => {x, y} Received on Thu Feb 28 2008 - 18:08:12 CET

Original text of this message