From: "Nick Roberts" <nickroberts@adaos.worldonline.co.uk>
Subject: Re: Side-Effects in Functions [Rosen Trick]
Date: Tue, 6 Nov 2001 22:48:42 -0000
Date: 2001-11-06T22:48:42+00:00 [thread overview]
Message-ID: <9s9pc2$125kn6$1@ID-25716.news.dfncis.de> (raw)
In-Reply-To: 87itcn8xxx.fsf@deneb.enyo.de
"Florian Weimer" <fw@deneb.enyo.de> wrote in message
news:87itcn8xxx.fsf@deneb.enyo.de...
> "Nick Roberts" <nickroberts@adaos.worldonline.co.uk> writes:
>
> > From a pedagogical point of view, care needs to be taken not to give the
> > impression that a function in a procedural programming language (most
> > programming languages, really) is the same thing as a mathematical
function.
> > Clearly it isn't: a mathematical function is a kind of relation called a
> > 'bijection' (and is nowadays specifically defined as such, I think);
>
> A function f : M -> N are two sets M, N and a subset G_f of the
> Cartesian product M x N with the following property: for all m in M,
> there exists exactly one n in N such that (m, n) in G_f.
That actually sounds like an injection to me (1 to 1), whereas I get the
impression mathematicians (discrete ones anyway ;-) tend to insist nowadays
on the definition of a function as a bijection (both 1 to 1 and 'onto', i.e.
both an injection and a surjection, so that f' is also a bijection). However
IANAM.
> > a programming function is really just an encapsulated computation.
>
> Yes, such functions take an additional implicit argument (the machine
> state before execution) and have an invisible result (the machine
> state after execution).
Neatly put. Of course, if the (programming) function might perform I/O, we
are potentially talking about 'world state' (or even 'universe state')
rather than just machine state! (And then we have the problem with enthalpy,
but that, as they say, is a different game of banana and clotted cream.)
> However, there are programming languages which use only mathematical
> functions, and a special construct for I/O, Haskell for example.
I'm not a Haskell expert, but functional languages in general do fix the
order of evaluation of their functions (or some of their functions)
precisely because of the side-effect problem. I presume lazy evaluation can
be a serious hazard, if used without care, nevertheless.
--
Nick Roberts
next prev parent reply other threads:[~2001-11-06 22:48 UTC|newest]
Thread overview: 166+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-11-02 3:56 List container strawman Ted Dennison
2001-11-02 4:20 ` James Rogers
2001-11-02 14:23 ` Ted Dennison
2001-11-02 14:38 ` Preben Randhol
2001-11-02 15:15 ` Larry Kilgallen
2001-11-02 4:35 ` Eric Merritt
2001-11-02 15:46 ` Ted Dennison
2001-11-02 7:28 ` Ehud Lamm
2001-11-02 14:57 ` Marin David Condic
2001-11-02 15:57 ` Francisco Javier Loma Daza
2001-11-02 16:28 ` Marin David Condic
2001-11-02 17:08 ` Ted Dennison
2001-11-02 15:06 ` Ted Dennison
2001-11-02 15:32 ` Marin David Condic
2001-11-02 16:33 ` Ted Dennison
2001-11-02 16:43 ` Marin David Condic
2001-11-02 22:51 ` Jeffrey Carter
2001-11-03 0:24 ` Matthew Heaney
2001-11-03 2:21 ` Jeffrey Carter
2001-11-03 22:51 ` Rosen Trick [List container strawman] Nick Roberts
2001-11-04 13:07 ` Robert Dewar
2001-11-04 17:17 ` Side-Effects in Functions [Rosen Trick] Nick Roberts
2001-11-05 2:46 ` Robert Dewar
2001-11-05 7:26 ` pete
2001-11-05 10:29 ` Dmitry A. Kazakov
2001-11-05 11:19 ` pete
2001-11-05 14:59 ` Dmitry A. Kazakov
2001-11-05 15:21 ` Preben Randhol
2001-11-05 16:04 ` Ted Dennison
2001-11-05 16:33 ` Dmitry A. Kazakov
2001-11-05 17:42 ` Warren W. Gay VE3WWG
2001-11-05 18:11 ` Preben Randhol
2001-11-06 8:38 ` Dmitry A. Kazakov
2001-11-06 9:31 ` tgingold
2001-11-06 0:10 ` Nick Roberts
2001-11-06 9:30 ` Dmitry A. Kazakov
2001-11-06 16:18 ` Lazy Evaluation [Side-Effects in Functions] Nick Roberts
2001-11-07 3:42 ` Robert Dewar
2001-11-07 4:42 ` Darren New
2001-11-07 11:54 ` Robert Dewar
2001-11-07 13:32 ` Florian Weimer
2001-11-07 13:24 ` Jean-Marc Bourguet
2001-11-09 18:06 ` Ted Dennison
2001-11-09 18:27 ` M. A. Alves
2001-11-11 20:13 ` Georg Bauhaus
2001-12-06 17:47 ` Harri J Haataja
2001-11-07 9:28 ` Dmitry A. Kazakov
2001-11-06 20:08 ` Side-Effects in Functions [Rosen Trick] Florian Weimer
2001-11-06 22:48 ` Nick Roberts [this message]
2001-11-07 10:46 ` Florian Weimer
2001-11-05 13:56 ` Robert Dewar
2001-11-05 16:08 ` Ted Dennison
2001-11-05 17:44 ` Warren W. Gay VE3WWG
2001-11-05 15:56 ` Ted Dennison
2001-11-05 18:46 ` Nick Roberts
2001-11-08 11:51 ` Georg Bauhaus
2001-11-16 0:31 ` List container strawman Vincent Marciante
2001-11-05 15:10 ` Marin David Condic
2001-11-05 18:31 ` Ted Dennison
2001-11-05 19:09 ` Marin David Condic
2001-11-05 21:23 ` Ted Dennison
2001-11-07 19:27 ` Stephen Leake
2001-11-02 18:11 ` Mark Johnson
2001-11-02 18:46 ` Marin David Condic
2001-11-02 19:21 ` Larry Kilgallen
2001-11-03 22:30 ` Nick Roberts
2001-11-02 16:26 ` Ted Dennison
2001-11-02 16:36 ` Marin David Condic
2001-11-02 19:31 ` Ted Dennison
2001-11-02 17:49 ` Jeffrey Carter
2001-11-08 10:34 ` Ehud Lamm
2001-11-08 18:53 ` Better Finalisation [List container strawman] Nick Roberts
2001-11-09 13:36 ` Robert Dewar
2001-11-09 15:04 ` Florian Weimer
2001-11-10 0:36 ` Nick Roberts
2001-11-09 15:16 ` Ted Dennison
2001-11-09 17:30 ` Better control of assignment Jeffrey Carter
2001-11-10 0:32 ` Nick Roberts
2001-11-10 22:27 ` Jeffrey Carter
2001-11-13 6:36 ` Craig Carey
2001-11-13 6:39 ` Craig Carey
2001-11-13 8:53 ` Craig Carey
2001-11-14 9:42 ` Craig Carey
2001-11-09 14:49 ` List container strawman Ted Dennison
2001-11-09 16:12 ` Ehud Lamm
2001-11-09 17:12 ` Marin David Condic
2001-11-09 18:11 ` Ted Dennison
2001-11-09 18:42 ` Matthew Heaney
2001-11-10 17:54 ` Simon Wright
[not found] ` <3BE29AF4.80804@telepath.com>
2001-11-02 13:14 ` Ted Dennison
2001-11-02 13:31 ` Larry Kilgallen
2001-11-02 15:09 ` Ted Dennison
2001-11-02 15:13 ` Preben Randhol
2001-11-02 20:48 ` David Starner
2001-11-02 22:49 ` Larry Kilgallen
2001-11-02 17:44 ` Jeffrey Carter
2001-11-02 20:07 ` Ted Dennison
2001-11-02 23:19 ` Jeffrey Carter
2001-11-03 6:56 ` Ted Dennison
2001-11-03 19:22 ` Jeffrey Carter
2001-11-04 18:58 ` Darren New
2001-11-04 19:40 ` Larry Kilgallen
2001-11-04 20:49 ` Darren New
2001-11-07 19:07 ` ramatthews
2001-11-08 0:04 ` Darren New
2001-11-08 4:50 ` Jeffrey Carter
2001-11-08 23:26 ` ramatthews
2001-11-09 18:00 ` Ted Dennison
2001-11-09 18:13 ` Jean-Marc Bourguet
2001-11-09 18:55 ` Ted Dennison
2001-11-10 1:48 ` Nick Roberts
2001-11-10 17:04 ` Ted Dennison
2001-11-10 20:59 ` Nick Roberts
2001-11-10 23:17 ` Larry Hazel
2001-11-11 3:27 ` Nick Roberts
2001-11-12 18:39 ` Darren New
2001-11-13 0:35 ` Nick Roberts
2001-11-10 19:36 ` Ehud Lamm
2001-11-10 20:15 ` Nick Roberts
2001-11-09 19:27 ` Larry Kilgallen
2001-11-09 20:03 ` Stephen Leake
2001-11-09 21:05 ` Ted Dennison
2001-11-09 22:42 ` Larry Kilgallen
2001-11-10 4:52 ` Nick Roberts
2001-11-10 20:24 ` ramatthews
2001-11-05 19:28 ` Ted Dennison
2001-11-05 19:42 ` Jean-Marc Bourguet
2001-11-05 20:40 ` Ted Dennison
2001-11-05 20:24 ` Darren New
2001-11-05 20:45 ` Ted Dennison
2001-11-05 17:21 ` List container strawman; Construct alternatives Stephen Leake
2001-11-03 7:42 ` List container strawman Simon Wright
2001-11-05 14:00 ` Stephen Leake
2001-11-08 11:17 ` Simon Wright
2001-11-13 16:29 ` Stephen Leake
2001-11-13 22:43 ` Jeffrey Carter
2001-11-13 22:48 ` Jeffrey Carter
2001-11-14 3:46 ` Nick Roberts
2001-11-15 10:23 ` Ehud Lamm
2001-11-14 14:50 ` Marin David Condic
2001-11-14 16:53 ` Jeffrey Carter
2001-11-14 17:59 ` Marin David Condic
2001-11-15 3:33 ` Nick Roberts
2001-11-15 15:10 ` Marin David Condic
2001-11-16 1:29 ` Nick Roberts
2001-11-16 16:03 ` Marin David Condic
2001-11-16 20:19 ` Nick Roberts
2001-11-15 18:08 ` Matthew Heaney
2001-11-02 14:49 ` Marin David Condic
2001-11-02 15:15 ` Ted Dennison
2001-11-02 15:37 ` Marin David Condic
2001-11-02 16:49 ` Ted Dennison
2001-11-02 17:09 ` Marin David Condic
2001-11-04 0:10 ` Nick Roberts
2001-11-03 23:41 ` Nick Roberts
2001-11-02 17:02 ` David Botton
2001-11-02 17:55 ` David Botton
2001-11-03 19:22 ` Nick Roberts
2001-11-08 14:57 ` M. A. Alves
2001-11-09 2:00 ` Jeffrey Carter
2001-11-09 18:31 ` Ted Dennison
2001-11-10 19:56 ` Ehud Lamm
-- strict thread matches above, loose matches on Subject: below --
2001-11-05 21:10 Side-Effects in Functions [Rosen Trick] Alexandre E. Kopilovitch
2001-11-05 21:58 ` Brian Rogoff
2001-11-22 6:22 ` David Thompson
2001-11-23 7:18 ` Brian Rogoff
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