a rank b array a; number b Example 1 : [ [( (x Dx)^2 + ( y Dy)^2) ( x Dx y Dy -1)] (x,y)] rank :: Example 2 : [ [( (x^3-y^2) Dx + 3 x^2) ( (x^3-y^2) Dy - 2 y)] (x,y)] rank ::
