#!/usr/bin/env python

# 11.1

import os, sys

sys.path += [os.getcwdu() + os.sep + ".." + os.sep + "python"]

import pylab as pl

from polyfuncs import poladd

def recursion(A, dA, C, dC, j):

    Fo, dFo = C, dC

    Eo, dEo = 1, 0

    A_z = A[1:dA+1]

    dA_z = dA-1

    zi, dzi = 1, 0

    for i in range(j-1):

        if dFo == 0:

            Fn1 = 0

        else:

            Fn1 = Fo[1:dFo+1]

        dFn1 = max(dFo-1, 0)

        Fn2 = -Fo[0]*A_z

        dFn2 = dA-1

        Fn, dFn = poladd(Fn1, dFn1, Fn2, dFn2)

        Fn = Fn.squeeze()

        zi = pl.convolve(zi,[0,1])

        dzi += 1

        En2 = Fn[0]*zi

        dEn2 = dzi

        En, dEn = poladd(Eo, dEo, En2, dEn2)

        En = En.squeeze()

        Eo, dEo = En, dEn

        Fo, dFo = Fn, dFn

    if dFo == 0:

        Fn1 = 0

    else:

        Fn1 = Fo[1:dFo+1]

    dFn1 = max(dFo-1, 0)

    Fn2 = -Fo[0]*A_z

    dFn2 = dA-1

    Fn, dFn = poladd(Fn1, dFn1, Fn2, dFn2)

    Fn = Fn.squeeze()

    Ej, dEj = Eo, dEo

    Fj, dFj = Fn, dFn

    return Fj, dFj, Ej, dEj