def test_dup_revert():
f = [-QQ(1, 720), QQ(0), QQ(1, 24), QQ(0), -QQ(1, 2), QQ(0), QQ(1)]
g = [QQ(61, 720), QQ(0), QQ(5, 24), QQ(0), QQ(1, 2), QQ(0), QQ(1)]
assert dup_revert(f, 8, QQ) == g
raises(NotReversible, lambda: dup_revert([QQ(1), QQ(0)], 3, QQ))
def test_dup_revert():
f = [-QQ(1, 720), QQ(0), QQ(1, 24), QQ(0), -QQ(1, 2), QQ(0), QQ(1)]
g = [QQ(61, 720), QQ(0), QQ(5, 24), QQ(0), QQ(1, 2), QQ(0), QQ(1)]
assert dup_revert(f, 8, QQ) == g
raises(NotReversible, lambda: dup_revert([QQ(1), QQ(0)], 3, QQ))
def revert(f, n):
"""Compute `f**(-1)` mod `x**n`. """
if not f.lev:
return f.per(dup_revert(f.rep, n, f.dom))
else:
raise ValueError('univariate polynomial expected')
def revert(f, n):
"""Compute `f**(-1)` mod `x**n`. """
if not f.lev:
return f.per(dup_revert(f.rep, n, f.dom))
else:
raise ValueError('univariate polynomial expected')