Source PostScript (symplan3d.pps)

%% syntaxe : M eqplan/plantype symplan3d --> M'
%% ou M' symetrique de M par rapport au plan P defini par eqplan/plantype
/symplan3d {
13 dict begin
   dup isplan {
      plan2eq /args exch def
   } {
      /args exch def
   } ifelse
   /z exch def
   /y exch def
   /x exch def
   args aload pop
   /d1 exch def
   /c1 exch def
   /b1 exch def
   /a1 exch def
   /n_U a1 dup mul b1 dup mul add c1 dup mul add sqrt def
   /a a1 n_U div def
   /b b1 n_U div def
   /c c1 n_U div def
   /d d1 n_U div def
   /u a x mul b y mul add c z mul add d add def
   x 2 a mul u mul sub
   y 2 b mul u mul sub
   z 2 c mul u mul sub
end
} def