再增添榕坚老师转来代码之前一段外文:
N_Poly4_Ma {
; newton's method applied to P(z) = (z + 1) * (z - 1) * (z - b + a) * (z - b - a)
; Parameter plane (M-set) for all 'a' and a specific 'b'
; F(z) = z - P(z)/P'(z)
; F(z) = (3*z^4 - 4*b*z^3 + (b^2-a^2-1)*z^2 + (b^2-a^2)) / ( 4*z^3 - 6*b*z^2 + 2*(b^2-a^2-1)*z + 2*b)
; Attractors: the 4 zeros of P(z): 1,-1, b+a, b-a
; Critical points: the 4 zeros, as well as
; b/2 +/- sqrt(3)*sqrt(b^2 + 2*a^2 + 2)/6
; For b=0, this reverts to the 'Newt_fang_xxx' formulas from pwc_convert.ufm
