[Om] invisible times and invisible plus

Paul Libbrecht paul at activemath.org
Mon Aug 31 14:27:45 CEST 2009

Jan Willem,

I think a mixed-fraction symbol would be very useful and meaning-ful.
But invisibletimes and invisibleplus really are not semantic-ful- 
enough to my taste.



PS: in activemath we have internal symbols for mixed fractions, not  
PPS: check MathML3, I vaguely remember it has a mixed-fraction concept  
at the core... or at least it was discussed.

Le 31-août-09 à 14:23, Jan Willem Knopper a écrit :

> Dear all,
> Is there a way to describe in OpenMath that a certain times or plus
> symbol is invisible ?
> For invisible times this would be something like 2a or 2(x+1) and for
> invisible plus I'm thinking about 1 1/2 (= 3/2).
> A lot of this has to do with presentation, but one might also argue  
> that
> numbers like 1+1/2 and 1 1/2 have different semantic meaning in  
> primary
> or highschool, where the integer part is written in front of the  
> fraction,
> rather than writing 3/2.
> Furthermore, for invisible plus, the use of the symbol would be
> binary, with as the first argument a positive integer (or maybe a
> variable) and as the second argument a fraction (of positive integers,
> or maybe variables).
> In the MathDox Formula Editor I would like to let the user input
> expressions with invisible times and invisible plus and it would be  
> nice
> to be able to store the information that they are invisible  
> (especially
> for invisible plus).
> Does anyone know how to describe expressions like 1 1/2 in OpenMath?
> Thanks in advance,
> Jan Willem
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