[pstricks] lines perpendicular and tangent to a bezier curve

[mathias legrand]

Hi all,

so far, I have something simple like:
\begin{pspicture}(0,-0.6)(6,4)
\psgrid
\psbezier[doubleline=true,doublesep=30pt,linewidth=1.5pt](0,-0.8)(-1.2,2.6)(-1.2,4.0)(5.8,4.0)
\psbezier[ArrowInsideNo=2,ArrowInside=-|,arrowscale=4,linewidth=1pt,linestyle=dashed,dash=2mm 
1mm](0,-0.8)(-1.2,2.6)(-1.2,4.0)(5.8,4.0)
\rput[r](0.1,-0.5){$(C)$}
\rput[l](1.8,-0.3){$(C')$}
\end{pspicture}

it looks like with the "ArrowInside=-|" command, it is possible to have 
access to a line which
is perpendicular to a bezier curve for a given intrinsic parameter with 
the "ArrowInsidePos" parameter.
I would like to have these lines more flexible in order to make them 
arrows or whatever.
The same with tangent lines would be great!
Is it easy to implement?

I had a look at pst-thick as well but it handles function-like curves 
only (nothing like psbezier or pscurve, unfortunately).