def test_polys():
x = Symbol("x")
ZZ = PythonIntegerRing()
QQ = SymPyRationalField()
for c in (Poly, Poly(x, x)):
check(c)
for c in (GFP, GFP([ZZ(1), ZZ(2), ZZ(3)], ZZ(7), ZZ)):
check(c)
for c in (DMP, DMP([ZZ(1), ZZ(2), ZZ(3)], 0, ZZ)):
check(c)
for c in (DMF, DMF(([ZZ(1), ZZ(2)], [ZZ(1), ZZ(3)], ZZ))):
check(c)
for c in (ANP, ANP([QQ(1), QQ(2)], [QQ(1), QQ(2), QQ(3)], QQ)):
check(c)
for c in (PythonIntegerRing, PythonIntegerRing()):
check(c)
for c in (SymPyIntegerRing, SymPyIntegerRing()):
check(c)
for c in (SymPyRationalField, SymPyRationalField()):
check(c)
for c in (PolynomialRing, PolynomialRing(ZZ, 'x', 'y')):
check(c)
for c in (FractionField, FractionField(ZZ, 'x', 'y')):
check(c)
for c in (ExpressionDomain, ExpressionDomain()):
check(c)
from sympy.polys.domains import HAS_FRACTION, HAS_GMPY
if HAS_FRACTION:
from sympy.polys.domains import PythonRationalField
for c in (PythonRationalField, PythonRationalField()):
check(c)
if HAS_GMPY:
from sympy.polys.domains import GMPYIntegerRing, GMPYRationalField
for c in (GMPYIntegerRing, GMPYIntegerRing()):
check(c)
for c in (GMPYRationalField, GMPYRationalField()):
check(c)
f = x**3 + x + 3
g = lambda x: x
for c in (RootOf, RootOf(f, 0), RootSum, RootSum(f, g)):
check(c)
def test_polys():
x = Symbol("X")
ZZ = PythonIntegerRing()
QQ = PythonRationalField()
for c in (Poly, Poly(x, x)):
check(c)
for c in (DMP, DMP([[ZZ(1)], [ZZ(2)], [ZZ(3)]], ZZ)):
check(c)
for c in (DMF, DMF(([ZZ(1), ZZ(2)], [ZZ(1), ZZ(3)]), ZZ)):
check(c)
for c in (ANP, ANP([QQ(1), QQ(2)], [QQ(1), QQ(2), QQ(3)], QQ)):
check(c)
for c in (PythonIntegerRing, PythonIntegerRing()):
check(c)
for c in (PythonRationalField, PythonRationalField()):
check(c)
for c in (PolynomialRing, PolynomialRing(ZZ, 'x', 'y')):
check(c)
for c in (FractionField, FractionField(ZZ, 'x', 'y')):
check(c)
for c in (ExpressionDomain, ExpressionDomain()):
check(c)
from sympy.core.compatibility import HAS_GMPY
if HAS_GMPY:
from sympy.polys.domains import GMPYIntegerRing, GMPYRationalField
for c in (GMPYIntegerRing, GMPYIntegerRing()):
check(c)
for c in (GMPYRationalField, GMPYRationalField()):
check(c)
f = x**3 + x + 3
g = exp
for c in (RootOf, RootOf(f, 0), RootSum, RootSum(f, g)):
check(c)
def minimal_polynomial(ex, x=None, compose=True, polys=False, domain=None):
"""
Computes the minimal polynomial of an algebraic element.
Parameters
==========
ex : Expr
Element or expression whose minimal polynomial is to be calculated.
x : Symbol, optional
Independent variable of the minimal polynomial
compose : boolean, optional (default=True)
Method to use for computing minimal polynomial. If ``compose=True``
(default) then ``_minpoly_compose`` is used, if ``compose=False`` then
groebner bases are used.
polys : boolean, optional (default=False)
If ``True`` returns a ``Poly`` object else an ``Expr`` object.
domain : Domain, optional
Ground domain
Notes
=====
By default ``compose=True``, the minimal polynomial of the subexpressions of ``ex``
are computed, then the arithmetic operations on them are performed using the resultant
and factorization.
If ``compose=False``, a bottom-up algorithm is used with ``groebner``.
The default algorithm stalls less frequently.
If no ground domain is given, it will be generated automatically from the expression.
Examples
========
>>> from sympy import minimal_polynomial, sqrt, solve, QQ
>>> from sympy.abc import x, y
>>> minimal_polynomial(sqrt(2), x)
x**2 - 2
>>> minimal_polynomial(sqrt(2), x, domain=QQ.algebraic_field(sqrt(2)))
x - sqrt(2)
>>> minimal_polynomial(sqrt(2) + sqrt(3), x)
x**4 - 10*x**2 + 1
>>> minimal_polynomial(solve(x**3 + x + 3)[0], x)
x**3 + x + 3
>>> minimal_polynomial(sqrt(y), x)
x**2 - y
"""
ex = sympify(ex)
if ex.is_number:
# not sure if it's always needed but try it for numbers (issue 8354)
ex = _mexpand(ex, recursive=True)
for expr in preorder_traversal(ex):
if expr.is_AlgebraicNumber:
compose = False
break
if x is not None:
x, cls = sympify(x), Poly
else:
x, cls = Dummy('x'), PurePoly
if not domain:
if ex.free_symbols:
domain = FractionField(QQ, list(ex.free_symbols))
else:
domain = QQ
if hasattr(domain, 'symbols') and x in domain.symbols:
raise GeneratorsError("the variable %s is an element of the ground "
"domain %s" % (x, domain))
if compose:
result = _minpoly_compose(ex, x, domain)
result = result.primitive()[1]
c = result.coeff(x**degree(result, x))
if c.is_negative:
result = expand_mul(-result)
return cls(result, x, field=True) if polys else result.collect(x)
if not domain.is_QQ:
raise NotImplementedError("groebner method only works for QQ")
result = _minpoly_groebner(ex, x, cls)
return cls(result, x, field=True) if polys else result.collect(x)
def minimal_polynomial(ex, x=None, **args):
"""
Computes the minimal polynomial of an algebraic element.
Parameters
==========
ex : algebraic element expression
x : independent variable of the minimal polynomial
Options
=======
compose : if ``True`` ``_minpoly_compose`` is used, if ``False`` the ``groebner`` algorithm
polys : if ``True`` returns a ``Poly`` object
domain : ground domain
Notes
=====
By default ``compose=True``, the minimal polynomial of the subexpressions of ``ex``
are computed, then the arithmetic operations on them are performed using the resultant
and factorization.
If ``compose=False``, a bottom-up algorithm is used with ``groebner``.
The default algorithm stalls less frequently.
If no ground domain is given, it will be generated automatically from the expression.
Examples
========
>>> from sympy import minimal_polynomial, sqrt, solve, QQ
>>> from sympy.abc import x, y
>>> minimal_polynomial(sqrt(2), x)
x**2 - 2
>>> minimal_polynomial(sqrt(2), x, domain=QQ.algebraic_field(sqrt(2)))
x - sqrt(2)
>>> minimal_polynomial(sqrt(2) + sqrt(3), x)
x**4 - 10*x**2 + 1
>>> minimal_polynomial(solve(x**3 + x + 3)[0], x)
x**3 + x + 3
>>> minimal_polynomial(sqrt(y), x)
x**2 - y
"""
from sympy.polys.polytools import degree
from sympy.polys.domains import FractionField
from sympy.core.basic import preorder_traversal
compose = args.get('compose', True)
polys = args.get('polys', False)
dom = args.get('domain', None)
ex = sympify(ex)
for expr in preorder_traversal(ex):
if expr.is_AlgebraicNumber:
compose = False
break
if x is not None:
x, cls = sympify(x), Poly
else:
x, cls = Dummy('x'), PurePoly
if not dom:
dom = FractionField(QQ, list(
ex.free_symbols)) if ex.free_symbols else QQ
if hasattr(dom, 'symbols') and x in dom.symbols:
raise GeneratorsError(
"the variable %s is an element of the ground domain %s" % (x, dom))
if compose:
result = _minpoly_compose(ex, x, dom)
result = result.primitive()[1]
c = result.coeff(x**degree(result, x))
if c.is_negative:
result = expand_mul(-result)
return cls(result, x, field=True) if polys else result.collect(x)
if not dom.is_QQ:
raise NotImplementedError("groebner method only works for QQ")
result = _minpoly_groebner(ex, x, cls)
return cls(result, x, field=True) if polys else result.collect(x)
def get_field(self):
"""Returns a field associated with `self`. """
from sympy.polys.domains import FractionField
return FractionField(self.dom, *self.gens)
def frac_field(self, *gens):
"""Returns a fraction field, i.e. `K(X)`. """
from sympy.polys.domains import FractionField
return FractionField(self, *gens)