pstricks-add redefines a lot of the pstricks macros.  
#
#  Do not load another PSTricks related package after pstricks-add!!
#
pstricks-add collects a lot of the code which was posted
to the pstricks mailing list and has some more new features:

- pstricks
   o random dots
   O braces
   o define and calculate colors on PS side
   o Gouraud shading
   o braces as node connection/linestyle
   o line style bar
   o lines, drawn "by hand"
   o arrows, arrows, arrows, ...

- pst-plot
   o new syntax for \psplot and \psparametricplot
   o new macro psTangentLine
   o new macro psplotTangent
   o new macro psplotDiffEqn

- pst-node
   o new option lineAngle for ncdiag
   o new macros for interpolation nodes
     and linear combination of two vectors
   o new macro ncbarr (line with 5 segments)


pstricks-add.pro    : the prolog file for pstricks-add
pstricks-add-doc.tex: the included doc file

Save the files pstricks-add.sty|pro|tex in a directory, 
which is part of your  local TeX tree. The pro file should go 
into $TEXMF/dvips/pstricks/
Then do not forget to run texhash to update this tree.
For more information  see the documentation of your LATEX distribution 
on installing packages into your local TeX system or read the 
TeX Frequently Asked Questions:
(http://www.tex.ac.uk/cgi-bin/texfaq2html?label=instpackages).