old_contents: # module 'poly' -- Polynomials
  
  # A polynomial is represented by a list of coefficients, e.g.,
  # [1, 10, 5] represents 1*x**0 + 10*x**1 + 5*x**2 (or 1 + 10x + 5x**2).
  # There is no way to suppress internal zeros; trailing zeros are
  # taken out by normalize().
  
  def normalize(p): # Strip unnecessary zero coefficients
  	n = len(p)
  	while p:
  		if p[n-1]: return p[:n]
  		n = n-1
  	return []
  
  def plus(a, b):
  	if len(a) < len(b): a, b = b, a # make sure a is the longest
  	res = a[:] # make a copy
  	for i in range(len(b)):
  		res[i] = res[i] + b[i]
  	return normalize(res)
  
  def minus(a, b):
  	if len(a) < len(b): a, b = b, a # make sure a is the longest
  	res = a[:] # make a copy
  	for i in range(len(b)):
  		res[i] = res[i] - b[i]
  	return normalize(res)
  
  def one(power, coeff): # Representation of coeff * x**power
  	res = []
  	for i in range(power): res.append(0)
  	return res + [coeff]
  
  def times(a, b):
  	res = []
  	for i in range(len(a)):
  		for j in range(len(b)):
  			res = plus(res, one(i+j, a[i]*b[j]))
  	return res
  
  def power(a, n): # Raise polynomial a to the positive integral power n
  	if n == 0: return [1]
  	if n == 1: return a
  	if n/2*2 == n:
  		b = power(a, n/2)
  		return times(b, b)
  	return times(power(a, n-1), a)
  
  def der(a): # First derivative
  	res = a[1:]
  	for i in range(len(res)):
  		res[i] = res[i] * (i+1)
  	return res
  
  # Computing a primitive function would require rational arithmetic...
  
new_contents: # module 'poly' -- Polynomials
  
  # A polynomial is represented by a list of coefficients, e.g.,
  # [1, 10, 5] represents 1*x**0 + 10*x**1 + 5*x**2 (or 1 + 10x + 5x**2).
  # There is no way to suppress internal zeros; trailing zeros are
  # taken out by normalize().
  
  def normalize(p): # Strip unnecessary zero coefficients
  	n = len(p)
  	while p:
  		if p[n-1]: return p[:n]
  		n = n-1
  	return []
  
  def plus(a, b):
  	if len(a) < len(b): a, b = b, a # make sure a is the longest
  	res = a[:] # make a copy
  	for i in range(len(b)):
  		res[i] = res[i] + b[i]
  	return normalize(res)
  
  def minus(a, b):
  	neg_b = map(lambda x: -x, b[:])
  	return plus(a, neg_b)
  
  def one(power, coeff): # Representation of coeff * x**power
  	res = []
  	for i in range(power): res.append(0)
  	return res + [coeff]
  
  def times(a, b):
  	res = []
  	for i in range(len(a)):
  		for j in range(len(b)):
  			res = plus(res, one(i+j, a[i]*b[j]))
  	return res
  
  def power(a, n): # Raise polynomial a to the positive integral power n
  	if n == 0: return [1]
  	if n == 1: return a
  	if n/2*2 == n:
  		b = power(a, n/2)
  		return times(b, b)
  	return times(power(a, n-1), a)
  
  def der(a): # First derivative
  	res = a[1:]
  	for i in range(len(res)):
  		res[i] = res[i] * (i+1)
  	return res
  
  # Computing a primitive function would require rational arithmetic...
  
subject: fix bug in poly.minus