Source PostScript (projxpath.pps)

%% syntaxe : path1 projxpath --> path2, projete orthogonal de path1
%% sur l'axe Ox
/projxpath {
1 dict begin
   /path1 exch def
   [
      path1 pathparamtable {} apply
      path1 pathpointstable {projx} papply
   ]
end
} def