Re: header part of the value?

From: Yagotta B. Kidding <ybk_at_mymail.com>
Date: Fri, 29 Feb 2008 00:58:09 +0100 (CET)
Message-ID: <Xns9A52C106AEFCAvdghher_at_194.177.96.26>


Jan Hidders <hidders_at_gmail.com> wrote in news:5dcfe1a9-3517-4315-8e27-cd7b5ba04674_at_e10g2000prf.googlegroups.com:

> On 28 feb, 18:08, "Yagotta B. Kidding" <y..._at_mymail.com> wrote:

>> Jan Hidders <hidd..._at_gmail.com> wrote in
>> news:2c892007-19bb-45ce-b73c-
>> 6cdc6c8de..._at_o77g2000hsf.googlegroups.com:
>>
>> > On 24 feb, 19:48, Marshall <marshall.spi..._at_gmail.com> 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
> e

>> function application:
>>
>> tuple = {(x, 1), (y, 2)}; first_el(tuple) => {x, y}
>
> That's not simple function application.

Why not ?

> 
> -- Jan Hidders
> 
Received on Fri Feb 29 2008 - 00:58:09 CET

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