> On 15 May 2016, at 19:32, Hans Åberg <haber...@telia.com> wrote:
>
>> On 15 May 2016, at 19:14, Hans Hagen <pra...@wxs.nl> wrote:
>>
>> On 5/15/2016 2:33 PM, Hans Åberg wrote:
>>> Maybe a way to distinguish between unary prefix operator “-“, and binary
>>> infix operator “-“: {} is interpreted as an empty operand, thus infix “-",
>>> whereas \relax is removed from the input meaning no operand, so prefix “-“.
>>> But \relax can have sub-/super-scripts, just as {}, and then in both cases,
>>> “–“ becomes binary:
>>>
>>> \startformula {}^2 - a \stopformula
>>> \startformula \relax^2 - a \stopformula
>>
>> why not use something more natural unicode
>>
>> \startformula \zwnj^2 - a \stopformula
>
> The TeX Book recommends using {} for superscripts to the lefts side, eg.
> \startformula {}_a^b C_d^e \stopformula
In addition to this usage, one can use {} for tensor-component notation:
\setupbodyfont[xits,10pt]
\setupmathematics[integral=nolimits]
The Ricci tensor
\startformula\relax
R^i{}_{ikj}
\stopformula
There might be module or page for tensor component notation, if somebody would
request it:
There is a standard ISO 80000-2 [1-2] for natural sciences and technology, but
not for pure math then, which I recall call for tensors expanded into
components to be typed in sans-serif. In pure math, one is using serifs as
always, with some other differences, usually sticking to a mathematically
complete description with summation signs and basis.
1. http://www.ise.ncsu.edu/jwilson/files/mathsigns.pdf
2. https://en.wikipedia.org/wiki/ISO_80000-2
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