Source PostScript (subticks.pps)

%% demi-longueur d'un sous-tiret (en point postscript)
/subticklength 1.25 def
/xsubtick {subticklength xt@ck} def
/ysubtick {subticklength yt@ck} def

/ysubtkstep .5 def
/setysubtkstep {
   /ysubtkstep exch def
} def

/xsubtkstep .5 def
/setxsubtkstep {
   /xsubtkstep exch def
} def

/setsubtkstep {
   setysubtkstep
   setxsubtkstep
} def

/xsubticks {
2 dict begin
   /n xmax xsubtkstep div truncate cvi 
      xsubtkstep mul def                        % subtick max
   /i xmin xsubtkstep div truncate cvi 
      xsubtkstep mul def                        % le 1er
   {
      i 0 ne {i xsubtick} if
      /i i xsubtkstep add store
      i n gt {exit} if
   } loop 
end
} def

/ysubticks {
2 dict begin
   /n ymax ysubtkstep div truncate cvi 
      ysubtkstep mul def                        % subtick max
   /i ymin ysubtkstep div truncate cvi 
      ysubtkstep mul def                        % l 1er
   {
      i 0 ne {i ysubtick} if
      /i i ysubtkstep add store
      i n gt {exit} if
   } loop 
end
} def

/subticks {
   xsubticks
   ysubticks
} def