def test_Domain_cyclotomic_field():
K = ZZ.cyclotomic_field(12)
assert K.ext.minpoly == Poly(cyclotomic_poly(12))
assert K.dom == QQ
F = QQ.cyclotomic_field(3)
assert F.ext.minpoly == Poly(cyclotomic_poly(3))
assert F.dom == QQ
E = F.cyclotomic_field(4)
assert field_isomorphism(E.ext, K.ext) is not None
assert E.dom == QQ
def roots_cyclotomic(f, factor=False):
"""Compute roots of cyclotomic polynomials. """
L, U = _inv_totient_estimate(f.degree())
for n in range(L, U + 1):
g = cyclotomic_poly(n, f.gen, polys=True)
if f == g:
break
else: # pragma: no cover
raise RuntimeError("failed to find index of a cyclotomic polynomial")
roots = []
if not factor:
# get the indices in the right order so the computed
# roots will be sorted
h = n//2
ks = [i for i in range(1, n + 1) if igcd(i, n) == 1]
ks.sort(key=lambda x: (x, -1) if x <= h else (abs(x - n), 1))
d = 2*I*pi/n
for k in reversed(ks):
roots.append(exp(k*d).expand(complex=True))
else:
g = Poly(f, extension=root(-1, n))
for h, _ in ordered(g.factor_list()[1]):
roots.append(-h.TC())
return roots
def roots_cyclotomic(f, factor=False):
"""Compute roots of cyclotomic polynomials. """
L, U = _inv_totient_estimate(f.degree())
for n in xrange(L, U + 1):
g = cyclotomic_poly(n, f.gen, polys=True)
if f == g:
break
else: # pragma: no cover
raise RuntimeError("failed to find index of a cyclotomic polynomial")
roots = []
if not factor:
for k in xrange(1, n + 1):
if igcd(k, n) == 1:
roots.append(exp(2*k*S.Pi*I/n).expand(complex=True))
else:
g = Poly(f, extension=(-1)**Rational(1, n))
for h, _ in g.factor_list()[1]:
roots.append(-h.TC())
return sorted(roots, key=default_sort_key)
def roots_cyclotomic(f, factor=False):
"""Compute roots of cyclotomic polynomials. """
L, U = _inv_totient_estimate(f.degree())
for n in xrange(L, U + 1):
g = cyclotomic_poly(n, f.gen, polys=True)
if f == g:
break
else: # pragma: no cover
raise RuntimeError("failed to find index of a cyclotomic polynomial")
roots = []
if not factor:
for k in xrange(1, n + 1):
if igcd(k, n) == 1:
roots.append(exp(2 * k * S.Pi * I / n).expand(complex=True))
else:
g = Poly(f, extension=(-1)**Rational(1, n))
for h, _ in g.factor_list()[1]:
roots.append(-h.TC())
return sorted(roots, key=default_sort_key)
def _minpoly_exp(ex, x):
"""
Returns the minimal polynomial of ``exp(ex)``
"""
c, a = ex.args[0].as_coeff_Mul()
if a == I * pi:
if c.is_rational:
q = sympify(c.q)
if c.p == 1 or c.p == -1:
if q == 3:
return x**2 - x + 1
if q == 4:
return x**4 + 1
if q == 6:
return x**4 - x**2 + 1
if q == 8:
return x**8 + 1
if q == 9:
return x**6 - x**3 + 1
if q == 10:
return x**8 - x**6 + x**4 - x**2 + 1
if q.is_prime:
s = 0
for i in range(q):
s += (-x)**i
return s
# x**(2*q) = product(factors)
factors = [cyclotomic_poly(i, x) for i in divisors(2 * q)]
mp = _choose_factor(factors, x, ex)
return mp
else:
raise NotAlgebraic("%s does not seem to be an algebraic element" %
ex)
raise NotAlgebraic("%s does not seem to be an algebraic element" % ex)
def _minpoly_exp(ex, x):
"""
Returns the minimal polynomial of ``exp(ex)``
"""
c, a = ex.args[0].as_coeff_Mul()
p = sympify(c.p)
q = sympify(c.q)
if a == I*pi:
if c.is_rational:
if c.p == 1 or c.p == -1:
if q == 3:
return x**2 - x + 1
if q == 4:
return x**4 + 1
if q == 6:
return x**4 - x**2 + 1
if q == 8:
return x**8 + 1
if q == 9:
return x**6 - x**3 + 1
if q == 10:
return x**8 - x**6 + x**4 - x**2 + 1
if q.is_prime:
s = 0
for i in range(q):
s += (-x)**i
return s
# x**(2*q) = product(factors)
factors = [cyclotomic_poly(i, x) for i in divisors(2*q)]
mp = _choose_factor(factors, x, ex)
return mp
else:
raise NotAlgebraic("%s doesn't seem to be an algebraic element" % ex)
raise NotAlgebraic("%s doesn't seem to be an algebraic element" % ex)
def test_cyclotomic_poly():
raises(ValueError, lambda: cyclotomic_poly(0, x))
assert cyclotomic_poly(1, x, polys=True) == Poly(x - 1)
assert cyclotomic_poly(1, x) == x - 1
assert cyclotomic_poly(2, x) == x + 1
assert cyclotomic_poly(3, x) == x**2 + x + 1
assert cyclotomic_poly(4, x) == x**2 + 1
assert cyclotomic_poly(5, x) == x**4 + x**3 + x**2 + x + 1
assert cyclotomic_poly(6, x) == x**2 - x + 1
def test_evalf_real_alg_num():
# This test demonstrates why the entry for `AlgebraicNumber` in
# `sympy.core.evalf._create_evalf_table()` has to use `x.to_root()`,
# instead of `x.as_expr()`. If the latter is used, then `z` will be
# a complex number with `0.e-20` for imaginary part, even though `a5`
# is a real number.
zeta = Symbol('zeta')
a5 = AlgebraicNumber(CRootOf(cyclotomic_poly(5), -1), [-1, -1, 0, 0],
alias=zeta)
z = a5.evalf()
assert isinstance(z, Float)
assert not hasattr(z, '_mpc_')
assert hasattr(z, '_mpf_')
def cyclotomic_field(self,
n,
ss=False,
alias="zeta",
gen=None,
root_index=-1):
r"""
Convenience method to construct a cyclotomic field.
Parameters
==========
n : int
Construct the nth cyclotomic field.
ss : boolean, optional (default=False)
If True, append *n* as a subscript on the alias string.
alias : str, optional (default="zeta")
Symbol name for the generator.
gen : :py:class:`~.Symbol`, optional (default=None)
Desired variable for the cyclotomic polynomial that defines the
field. If ``None``, a dummy variable will be used.
root_index : int, optional (default=-1)
Specifies which root of the polynomial is desired. The ordering is
as defined by the :py:class:`~.ComplexRootOf` class. The default of
``-1`` selects the root $\mathrm{e}^{2\pi i/n}$.
Examples
========
>>> from sympy import QQ, latex
>>> K = QQ.cyclotomic_field(5)
>>> K.to_sympy(K([-1, 1]))
1 - zeta
>>> L = QQ.cyclotomic_field(7, True)
>>> a = L.to_sympy(L([-1, 1]))
>>> print(a)
1 - zeta7
>>> print(latex(a))
1 - \zeta_{7}
"""
from sympy.polys.specialpolys import cyclotomic_poly
if ss:
alias += str(n)
return self.alg_field_from_poly(cyclotomic_poly(n, gen),
alias=alias,
root_index=root_index)
