Re: what are keys and surrogates?
From: mAsterdam <mAsterdam_at_vrijdag.org>
Date: Mon, 28 Jan 2008 01:26:52 +0100
Message-ID: <479d20c6$0$85787$e4fe514c_at_news.xs4all.nl>
>
> It's good in that it states what we often informally mean by "function".
>
> It's bad in that it isn't formal, and therefore, not exact; what is a rule?
> A more serious problem is that it doesn't correspond to what mathematicians
> mean by a function, namely, an assignment to each member of a set A
> of exactly one member of a set B. The difference becomes clear when you
> ask on which grounds two functions are considered to be the same function.
> Finally, it doesn't mention that many authors use the term "function"
> for a partial function, i.e. an assignment to 0 or more members of set A.
Date: Mon, 28 Jan 2008 01:26:52 +0100
Message-ID: <479d20c6$0$85787$e4fe514c_at_news.xs4all.nl>
rpost schreef:
> vldm10 wrote:
>
>> Definition1 A function from A to B is a rule that assigns, to each >> member of set A, exactly one member of set B. >> >> Is this good or bad definition for a function?
>
> It's good in that it states what we often informally mean by "function".
>
> It's bad in that it isn't formal, and therefore, not exact; what is a rule?
> A more serious problem is that it doesn't correspond to what mathematicians
> mean by a function, namely, an assignment to each member of a set A
> of exactly one member of a set B. The difference becomes clear when you
> ask on which grounds two functions are considered to be the same function.
> Finally, it doesn't mention that many authors use the term "function"
> for a partial function, i.e. an assignment to 0 or more members of set A.
Hi Reinier, please see the 'Function' thread for more on this. The fact that I already posted a new version of the glossary does not mean that improvements aren't welcome. Received on Mon Jan 28 2008 - 01:26:52 CET