User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:24.0) Gecko/20100101
            Thunderbird/24.5.0
MIME-Version: 1.0
References: <539432A6.7030205@clear.net.nz> <5395A7A3.7040106@residenset.net>
Content-Type: text/plain; charset=ISO-8859-1
Message-ID:  <5395AA02.8040704@morningstar2.co.uk>
Date:         Mon, 9 Jun 2014 13:35:14 +0100
Reply-To: Mailing list for the LaTeX3 project
              <LATEX-L@LISTSERV.UNI-HEIDELBERG.DE>
Sender: Mailing list for the LaTeX3 project <LATEX-L@LISTSERV.UNI-HEIDELBERG.DE>
From: Joseph Wright <joseph.wright@MORNINGSTAR2.CO.UK>
Subject: Re: Juxtaposition in l3fp
To: LATEX-L@LISTSERV.UNI-HEIDELBERG.DE
In-Reply-To:  <5395A7A3.7040106@residenset.net>
Precedence: list
Content-Transfer-Encoding: quoted-printable
Envelope-To: <rainer.schoepf@GMX.NET>
Status: R

On 09/06/2014 13:25, Lars Hellstr=F6m wrote:
> aparsloe skrev 2014-06-08 11.53:
>> Should l3fp use juxtaposition *at all* to indicate multiplication? I
>> am an
>> enthusiast for l3fp. I am using it constantly (in LyX using LyX's inst=
ant
>> preview to evaluate formulas), but that has simply heightened my uneas=
e
>> about using juxtaposition to indicate multiplication, particularly as
>> part
>> of a kernel package.
>=20
> Syntactic sugar: may look like yum, but it can hurt you. :-)
>=20
>> Most people using numbers have their mental reflexes shaped either by
>> mathematical usage or calculator or spreadsheet usage. The last two,
>> to my
>> knowledge, don't allow juxtaposition. Multiplication must be explicitl=
y
>> indicated with an asterisk.
>=20
> You conspicuously omit programming languages, which I would put as a
> forerunner of spreadsheets (the less about said, the better), and
> probably also of modern calculators that attempt to display formulae. S=
o
> it probably all boils down to "because that's how it was in FORTRAN"
> (which, if memory serves, ignored spaces).
>=20
> A data point of possible interest is MetaFont, which has some cases of
> juxtaposition as a high priority operation (e.g. 2/3x means two thirds
> of x). Since it's Knuth, it's probably very consistent, but not
> necessarily intuitive.
>=20
>> Mathematical usage is variable and often irregular
>=20
> Oh yes. One of the really big mistakes people make when trying to
> implement mathematics is believing that the mathematical formula
> language is consistent, just because it is precise. Juxtaposition can
> denote pretty much *anything* (depending on context), and because
> juxtaposition is multiplication, it follows that pretty much anything
> can be regarded as a kind of multiplication. ;-)
>=20
> Lars Hellstr=F6m

I guess Bruno can say more, but I suspect that requiring explicit "*"
for multiplication might have a benefit in terms of code complexity (no
need to allow for other cases). An obvious question for me is would such
a position lead to problematic cases? The comparison with MetaFont is
probably a useful one in this regard.
--=20
Joseph Wright