class POINT

inherit ANY
  redefine out
end

creation
  make

feature
  x,y : REAL
        -- the coordinates of the point

left_of ( p, q: like Current ) : BOOLEAN is
  	-- Is Current to left of directed line pq?
  local
    a, b, c, d : REAL
  do

    a := p.y - q.y
    b := q.x - p.x
    c := x - p.x
    d := y - p.y

    Result := (a*c + b*d > 0)

-- std_error . put_string ( "Result of left_of with Current = " )
-- std_error . put_string ( Current.out )
-- std_error . put_new_line
-- std_error . put_string ( "%Np = " )
-- std_error . put_string ( p.out )
-- std_error . put_string ( "  q = " )
-- std_error . put_string ( q.out )
-- std_error . put_string ( "%N is " + Result.out + "%N" )

  end
 
prefix "-" : like Current is
  do
    !! Result.make ( -x, -y )
  end

out : STRING is
  do
    Result := x.out + " " + y.out
  end

feature {NONE}

make (a,b: REAL) is
  do
    x := a
    y := b
  end

end -- class POINT