[pstricks] Arrows in math equation?

[Carsten Vogel]

Anton Suchaneck schrieb:
> Hello,
>
% needs \usepackage{pst-node}

% w/o pspicture-environment nodes would
% reference the baseline. ~ = emptyspace
\[\rnode{start}{\vphantom{1em}~}\ln(a^{\rnode{end}{b}})\]
\ncbar[angle=90,arm=.3em,nodesep=.2em]{<-}{start}{end}

> an arrow from above the "b" to the empty space infront of the "\ln"
> Is that doable?
Affirmative.