The pmathx module extends pmathml with some
further default elements and some further math constructs.
Some of these are experimental. Currently the extensions include:
infix superscript and subscript operators, sub, sup
and subsup
and infix over and under operators, over, under and
underover
set construction operators setl <mrow-contents>
and setp <math-object> <math-object>.
fenced absolute-value operator abs <math-object>.
overline and underline operators
overline <math-object>, underline <math-object>.
series operator series <math-object> <math-object> <mrow-content>.
factorial operator <mrow-content> factorial .
further token elements: supremum, supremum, infimum,
cf, divides, log, ln, exp, sin, cos,
tan, sinh, cosh, tanh, max, min,
lim. There may be others, and it is easy to define others.