> Hans Åberg <mailto:haberg-1@telia.com>
> 15. Mai 2016 um 16:28
>
> Traditionally constants are set in upright and variables in italic. So 
> constants like “log” etc., are set in upright. It is not used 
> rigorously because of past typographical limitations, but one might in 
> principle do that, cf. the example below, where the integral 
> differential “d” is set in upright to disambiguate relative the 
> function named “d”.
>
> When Unicode added math styles, it added italics, expecting the ASCII 
> range to be upright, which would be normal if using a text editor that 
> does not translate math into italics. But the TeX legacy is the opposite.
>
> ----
> \setupbodyfont[xits,10pt]
>
> \startformula
> \startalign
> I &= ∫_S d(x)\, dx \NR
> I &= ∫_S 𝑑(x)\, dx \NR
> I &= ∫_S d(x)\, \mathupright{d} x \NR
> I &= ∫_S 𝑑(x)\, \mathupright{d} x \NR
> \stopalign
> \stopformula
> ----
\appendtoks \rm \to \everymathematics

\setupbodyfont[xits,10pt]

\starttext

\startformula
     \startmathalignment
     \NC I \EQ ∫_S d(x)\, dx \NR
     \NC I \EQ ∫_S 𝑑(x)\, dx \NR
     \NC I \EQ ∫_S d(x)\, dx \NR
     \NC I \EQ ∫_S 𝑑(x)\, dx \NR
     \stopmathalignment
\stopformula

\stoptext

Wolfgang