On 09/06/2014 13:25, Lars Hellström wrote:
> aparsloe skrev 20140608 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 instant
>> preview to evaluate formulas), but that has simply heightened my unease
>> about using juxtaposition to indicate multiplication, particularly as
>> part
>> of a kernel package.
>
> Syntactic sugar: may look like yum, but it can hurt you. :)
>
>> 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 explicitly
>> indicated with an asterisk.
>
> 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. So
> it probably all boils down to "because that's how it was in FORTRAN"
> (which, if memory serves, ignored spaces).
>
> 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.
>
>> Mathematical usage is variable and often irregular
>
> 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. ;)
>
> Lars Hellström
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.

Joseph Wright
