%require "common.ps"

/ptrn { % <x1> <y1> <x2> <y2> ... <xn> <yn> ptrn -
   % first draw an bullet at first coordinate
   count dup 2 sub roll
   2 copy
      newpath 2 0 360 arc F
      M

   count 0 gt {  % is there more than one point?
      % then a line for all but the last
      count 2 idiv 1 sub {
         count dup 2 sub roll L
      } repeat

      % only the last one left, where the arrow-head must be
      7 dict begin
         /y exch def
         /x exch def
         currentpoint y sub neg /dy exch def
         x sub neg /dx exch def

         /al dx dx mul dy dy mul add sqrt def
         /angle dy dx atan def
         /b al 7 sub def

         gsave
            currentpoint translate
            angle rotate
            b 0 L S
            b -2.5 M b 2.5 L al 0 L CP F  % arrow head
         grestore
      end
   } if
} def


% <x1> <y> <x2> ptr1 -
/ptr1 { 1 index ptrn } def