%N pgarro %F $MIR/src/pgarro.f
%D Draw an arrow
%B
      SUBROUTINE PGARRO (X1, Y1, X2, Y2)
      REAL X1, Y1, X2, Y2

 Draw an arrow from the point with world-coordinates (X1,Y1) to 
 (X2,Y2). The size of the arrowhead at (X2,Y2) is determined by 
 the current character size set by routine PGSCH. The default size 
 is 1/40th of the smaller of the width or height of the view surface.
 The appearance of the arrowhead (shape and solid or open) is
 controlled by routine PGSAH.

 Arguments:
  X1, Y1 (input)  : world coordinates of the tail of the arrow.
  X2, Y2 (input)  : world coordinates of the head of the arrow.
