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Re: Binary Relations, draft 1

Concernant « Re: Binary Relations, draft 1 », Joerg Knappen écrit : «
» IMHO the rule for upright setting is, that (beside some other entities)
» _numbers_ are typeset upright. Note that it is not _constants_, since any
» ad hoc constants (typically denoted by $c$ or $k$) are typeset in math 
» italics. 

Ah, that's not so simple...

Most maths "constants" are indeed unknown functions.

But, with H. Aberg's rule, we would have to distinguish between:

 Let $f$ be a continuous function (math ital)

and
 
 Let $f(x)=\exp(x^2)$  (f should be upright, as it will be of constant
meaning thereafter, whereas x should me math ital)

And now, an effectiveness theorem would simply be the uprightification
of some constant.

Now, the "number" 5 maybe equal to 1 or even 0 depending on the
charasteristic of the number field it lives in, so it may be seen as a
variable depending on that charasteristic!

What we really need is a Javascript implementation of dynamical fonts
in PDF, moving from italic to upright and back, endlessly!

Thierry Bouche, Grenoble.

PS It has been the custom in France to typeset capitals upright in
maths, and lowercase i italic. I'm afraid this was more aesthetical
than semantic. 
PPS I didn't change my mind during the night;-)