prjycq8up
/
image-handler
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity
You can not select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
Branches Tags
${ item.name }
Create tag ${ searchTerm }
Create branch ${ searchTerm }
from '1cf58eadb3'
${ noResults }
image-handler/image-handler10.0/venv/lib/site-packages/sympy/polys/domains/domain.py

1305 lines
37 KiB
Raw Normal View History Unescape

first commit
5 months ago
"""Implementation of :class:`Domain` class. """
from __future__ import annotations
from typing import Any
from sympy.core.numbers import AlgebraicNumber
from sympy.core import Basic, sympify
from sympy.core.sorting import default_sort_key, ordered
from sympy.external.gmpy import HAS_GMPY
from sympy.polys.domains.domainelement import DomainElement
from sympy.polys.orderings import lex
from sympy.polys.polyerrors import UnificationFailed, CoercionFailed, DomainError
from sympy.polys.polyutils import _unify_gens, _not_a_coeff
from sympy.utilities import public
from sympy.utilities.iterables import is_sequence
@public
class Domain:
"""Superclass for all domains in the polys domains system.
See :ref:`polys-domainsintro` for an introductory explanation of the
domains system.
The :py:class:`~.Domain` class is an abstract base class for all of the
concrete domain types. There are many different :py:class:`~.Domain`
subclasses each of which has an associated ``dtype`` which is a class
representing the elements of the domain. The coefficients of a
:py:class:`~.Poly` are elements of a domain which must be a subclass of
:py:class:`~.Domain`.
Examples
========
The most common example domains are the integers :ref:`ZZ` and the
rationals :ref:`QQ`.
>>> from sympy import Poly, symbols, Domain
>>> x, y = symbols('x, y')
>>> p = Poly(x**2 + y)
>>> p
Poly(x**2 + y, x, y, domain='ZZ')
>>> p.domain
ZZ
>>> isinstance(p.domain, Domain)
True
>>> Poly(x**2 + y/2)
Poly(x**2 + 1/2*y, x, y, domain='QQ')
The domains can be used directly in which case the domain object e.g.
(:ref:`ZZ` or :ref:`QQ`) can be used as a constructor for elements of
``dtype``.
>>> from sympy import ZZ, QQ
>>> ZZ(2)
2
>>> ZZ.dtype # doctest: +SKIP
<class 'int'>
>>> type(ZZ(2)) # doctest: +SKIP
<class 'int'>
>>> QQ(1, 2)
1/2
>>> type(QQ(1, 2)) # doctest: +SKIP
<class 'sympy.polys.domains.pythonrational.PythonRational'>
The corresponding domain elements can be used with the arithmetic
operations ``+,-,*,**`` and depending on the domain some combination of
``/,//,%`` might be usable. For example in :ref:`ZZ` both ``//`` (floor
division) and ``%`` (modulo division) can be used but ``/`` (true
division) cannot. Since :ref:`QQ` is a :py:class:`~.Field` its elements
can be used with ``/`` but ``//`` and ``%`` should not be used. Some
domains have a :py:meth:`~.Domain.gcd` method.
>>> ZZ(2) + ZZ(3)
5
>>> ZZ(5) // ZZ(2)
2
>>> ZZ(5) % ZZ(2)
1
>>> QQ(1, 2) / QQ(2, 3)
3/4
>>> ZZ.gcd(ZZ(4), ZZ(2))
2
>>> QQ.gcd(QQ(2,7), QQ(5,3))
1/21
>>> ZZ.is_Field
False
>>> QQ.is_Field
True
There are also many other domains including:
1. :ref:`GF(p)` for finite fields of prime order.
2. :ref:`RR` for real (floating point) numbers.
3. :ref:`CC` for complex (floating point) numbers.
4. :ref:`QQ(a)` for algebraic number fields.
5. :ref:`K[x]` for polynomial rings.
6. :ref:`K(x)` for rational function fields.
7. :ref:`EX` for arbitrary expressions.
Each domain is represented by a domain object and also an implementation
class (``dtype``) for the elements of the domain. For example the
:ref:`K[x]` domains are represented by a domain object which is an
instance of :py:class:`~.PolynomialRing` and the elements are always
instances of :py:class:`~.PolyElement`. The implementation class
represents particular types of mathematical expressions in a way that is
more efficient than a normal SymPy expression which is of type
:py:class:`~.Expr`. The domain methods :py:meth:`~.Domain.from_sympy` and
:py:meth:`~.Domain.to_sympy` are used to convert from :py:class:`~.Expr`
to a domain element and vice versa.
>>> from sympy import Symbol, ZZ, Expr
>>> x = Symbol('x')
>>> K = ZZ[x] # polynomial ring domain
>>> K
ZZ[x]
>>> type(K) # class of the domain
<class 'sympy.polys.domains.polynomialring.PolynomialRing'>
>>> K.dtype # class of the elements
<class 'sympy.polys.rings.PolyElement'>
>>> p_expr = x**2 + 1 # Expr
>>> p_expr
x**2 + 1
>>> type(p_expr)
<class 'sympy.core.add.Add'>
>>> isinstance(p_expr, Expr)
True
>>> p_domain = K.from_sympy(p_expr)
>>> p_domain # domain element
x**2 + 1
>>> type(p_domain)
<class 'sympy.polys.rings.PolyElement'>
>>> K.to_sympy(p_domain) == p_expr
True
The :py:meth:`~.Domain.convert_from` method is used to convert domain
elements from one domain to another.
>>> from sympy import ZZ, QQ
>>> ez = ZZ(2)
>>> eq = QQ.convert_from(ez, ZZ)
>>> type(ez) # doctest: +SKIP
<class 'int'>
>>> type(eq) # doctest: +SKIP
<class 'sympy.polys.domains.pythonrational.PythonRational'>
Elements from different domains should not be mixed in arithmetic or other
operations: they should be converted to a common domain first. The domain
method :py:meth:`~.Domain.unify` is used to find a domain that can
represent all the elements of two given domains.
>>> from sympy import ZZ, QQ, symbols
>>> x, y = symbols('x, y')
>>> ZZ.unify(QQ)
QQ
>>> ZZ[x].unify(QQ)
QQ[x]
>>> ZZ[x].unify(QQ[y])
QQ[x,y]
If a domain is a :py:class:`~.Ring` then is might have an associated
:py:class:`~.Field` and vice versa. The :py:meth:`~.Domain.get_field` and
:py:meth:`~.Domain.get_ring` methods will find or create the associated
domain.
>>> from sympy import ZZ, QQ, Symbol
>>> x = Symbol('x')
>>> ZZ.has_assoc_Field
True
>>> ZZ.get_field()
QQ
>>> QQ.has_assoc_Ring
True
>>> QQ.get_ring()
ZZ
>>> K = QQ[x]
>>> K
QQ[x]
>>> K.get_field()
QQ(x)
See also
========
DomainElement: abstract base class for domain elements
construct_domain: construct a minimal domain for some expressions
"""
dtype: type | None = None
"""The type (class) of the elements of this :py:class:`~.Domain`:
>>> from sympy import ZZ, QQ, Symbol
>>> ZZ.dtype
<class 'int'>
>>> z = ZZ(2)
>>> z
2
>>> type(z)
<class 'int'>
>>> type(z) == ZZ.dtype
True
Every domain has an associated **dtype** ("datatype") which is the
class of the associated domain elements.
See also
========
of_type
"""
zero: Any = None
"""The zero element of the :py:class:`~.Domain`:
>>> from sympy import QQ
>>> QQ.zero
0
>>> QQ.of_type(QQ.zero)
True
See also
========
of_type
one
"""
one: Any = None
"""The one element of the :py:class:`~.Domain`:
>>> from sympy import QQ
>>> QQ.one
1
>>> QQ.of_type(QQ.one)
True
See also
========
of_type
zero
"""
is_Ring = False
"""Boolean flag indicating if the domain is a :py:class:`~.Ring`.
>>> from sympy import ZZ
>>> ZZ.is_Ring
True
Basically every :py:class:`~.Domain` represents a ring so this flag is
not that useful.
See also
========
is_PID
is_Field
get_ring
has_assoc_Ring
"""
is_Field = False
"""Boolean flag indicating if the domain is a :py:class:`~.Field`.
>>> from sympy import ZZ, QQ
>>> ZZ.is_Field
False
>>> QQ.is_Field
True
See also
========
is_PID
is_Ring
get_field
has_assoc_Field
"""
has_assoc_Ring = False
"""Boolean flag indicating if the domain has an associated
:py:class:`~.Ring`.
>>> from sympy import QQ
>>> QQ.has_assoc_Ring
True
>>> QQ.get_ring()
ZZ
See also
========
is_Field
get_ring
"""
has_assoc_Field = False
"""Boolean flag indicating if the domain has an associated
:py:class:`~.Field`.
>>> from sympy import ZZ
>>> ZZ.has_assoc_Field
True
>>> ZZ.get_field()
QQ
See also
========
is_Field
get_field
"""
is_FiniteField = is_FF = False
is_IntegerRing = is_ZZ = False
is_RationalField = is_QQ = False
is_GaussianRing = is_ZZ_I = False
is_GaussianField = is_QQ_I = False
is_RealField = is_RR = False
is_ComplexField = is_CC = False
is_AlgebraicField = is_Algebraic = False
is_PolynomialRing = is_Poly = False
is_FractionField = is_Frac = False
is_SymbolicDomain = is_EX = False
is_SymbolicRawDomain = is_EXRAW = False
is_FiniteExtension = False
is_Exact = True
is_Numerical = False
is_Simple = False
is_Composite = False
is_PID = False
"""Boolean flag indicating if the domain is a `principal ideal domain`_.
>>> from sympy import ZZ
>>> ZZ.has_assoc_Field
True
>>> ZZ.get_field()
QQ
.. _principal ideal domain: https://en.wikipedia.org/wiki/Principal_ideal_domain
See also
========
is_Field
get_field
"""
has_CharacteristicZero = False
rep: str | None = None
alias: str | None = None
def __init__(self):
raise NotImplementedError
def __str__(self):
return self.rep
def __repr__(self):
return str(self)
def __hash__(self):
return hash((self.__class__.__name__, self.dtype))
def new(self, *args):
return self.dtype(*args)
@property
def tp(self):
"""Alias for :py:attr:`~.Domain.dtype`"""
return self.dtype
def __call__(self, *args):
"""Construct an element of ``self`` domain from ``args``. """
return self.new(*args)
def normal(self, *args):
return self.dtype(*args)
def convert_from(self, element, base):
"""Convert ``element`` to ``self.dtype`` given the base domain. """
if base.alias is not None:
method = "from_" + base.alias
else:
method = "from_" + base.__class__.__name__
_convert = getattr(self, method)
if _convert is not None:
result = _convert(element, base)
if result is not None:
return result
raise CoercionFailed("Cannot convert %s of type %s from %s to %s" % (element, type(element), base, self))
def convert(self, element, base=None):
"""Convert ``element`` to ``self.dtype``. """
if base is not None:
if _not_a_coeff(element):
raise CoercionFailed('%s is not in any domain' % element)
return self.convert_from(element, base)
if self.of_type(element):
return element
if _not_a_coeff(element):
raise CoercionFailed('%s is not in any domain' % element)
from sympy.polys.domains import ZZ, QQ, RealField, ComplexField
if ZZ.of_type(element):
return self.convert_from(element, ZZ)
if isinstance(element, int):
return self.convert_from(ZZ(element), ZZ)
if HAS_GMPY:
integers = ZZ
if isinstance(element, integers.tp):
return self.convert_from(element, integers)
rationals = QQ
if isinstance(element, rationals.tp):
return self.convert_from(element, rationals)
if isinstance(element, float):
parent = RealField(tol=False)
return self.convert_from(parent(element), parent)
if isinstance(element, complex):
parent = ComplexField(tol=False)
return self.convert_from(parent(element), parent)
if isinstance(element, DomainElement):
return self.convert_from(element, element.parent())
# TODO: implement this in from_ methods
if self.is_Numerical and getattr(element, 'is_ground', False):
return self.convert(element.LC())
if isinstance(element, Basic):
try:
return self.from_sympy(element)
except (TypeError, ValueError):
pass
else: # TODO: remove this branch
if not is_sequence(element):
try:
element = sympify(element, strict=True)
if isinstance(element, Basic):
return self.from_sympy(element)
except (TypeError, ValueError):
pass
raise CoercionFailed("Cannot convert %s of type %s to %s" % (element, type(element), self))
def of_type(self, element):
"""Check if ``a`` is of type ``dtype``. """
return isinstance(element, self.tp) # XXX: this isn't correct, e.g. PolyElement
def __contains__(self, a):
"""Check if ``a`` belongs to this domain. """
try:
if _not_a_coeff(a):
raise CoercionFailed
self.convert(a) # this might raise, too
except CoercionFailed:
return False
return True
def to_sympy(self, a):
"""Convert domain element *a* to a SymPy expression (Expr).
Explanation
===========
Convert a :py:class:`~.Domain` element *a* to :py:class:`~.Expr`. Most
public SymPy functions work with objects of type :py:class:`~.Expr`.
The elements of a :py:class:`~.Domain` have a different internal
representation. It is not possible to mix domain elements with
:py:class:`~.Expr` so each domain has :py:meth:`~.Domain.to_sympy` and
:py:meth:`~.Domain.from_sympy` methods to convert its domain elements
to and from :py:class:`~.Expr`.
Parameters
==========
a: domain element
An element of this :py:class:`~.Domain`.
Returns
=======
expr: Expr
A normal SymPy expression of type :py:class:`~.Expr`.
Examples
========
Construct an element of the :ref:`QQ` domain and then convert it to
:py:class:`~.Expr`.
>>> from sympy import QQ, Expr
>>> q_domain = QQ(2)
>>> q_domain
2
>>> q_expr = QQ.to_sympy(q_domain)
>>> q_expr
2
Although the printed forms look similar these objects are not of the
same type.
>>> isinstance(q_domain, Expr)
False
>>> isinstance(q_expr, Expr)
True
Construct an element of :ref:`K[x]` and convert to
:py:class:`~.Expr`.
>>> from sympy import Symbol
>>> x = Symbol('x')
>>> K = QQ[x]
>>> x_domain = K.gens[0] # generator x as a domain element
>>> p_domain = x_domain**2/3 + 1
>>> p_domain
1/3*x**2 + 1
>>> p_expr = K.to_sympy(p_domain)
>>> p_expr
x**2/3 + 1
The :py:meth:`~.Domain.from_sympy` method is used for the opposite
conversion from a normal SymPy expression to a domain element.
>>> p_domain == p_expr
False
>>> K.from_sympy(p_expr) == p_domain
True
>>> K.to_sympy(p_domain) == p_expr
True
>>> K.from_sympy(K.to_sympy(p_domain)) == p_domain
True
>>> K.to_sympy(K.from_sympy(p_expr)) == p_expr
True
The :py:meth:`~.Domain.from_sympy` method makes it easier to construct
domain elements interactively.
>>> from sympy import Symbol
>>> x = Symbol('x')
>>> K = QQ[x]
>>> K.from_sympy(x**2/3 + 1)
1/3*x**2 + 1
See also
========
from_sympy
convert_from
"""
raise NotImplementedError
def from_sympy(self, a):
"""Convert a SymPy expression to an element of this domain.
Explanation
===========
See :py:meth:`~.Domain.to_sympy` for explanation and examples.
Parameters
==========
expr: Expr
A normal SymPy expression of type :py:class:`~.Expr`.
Returns
=======
a: domain element
An element of this :py:class:`~.Domain`.
See also
========
to_sympy
convert_from
"""
raise NotImplementedError
def sum(self, args):
return sum(args)
def from_FF(K1, a, K0):
"""Convert ``ModularInteger(int)`` to ``dtype``. """
return None
def from_FF_python(K1, a, K0):
"""Convert ``ModularInteger(int)`` to ``dtype``. """
return None
def from_ZZ_python(K1, a, K0):
"""Convert a Python ``int`` object to ``dtype``. """
return None
def from_QQ_python(K1, a, K0):
"""Convert a Python ``Fraction`` object to ``dtype``. """
return None
def from_FF_gmpy(K1, a, K0):
"""Convert ``ModularInteger(mpz)`` to ``dtype``. """
return None
def from_ZZ_gmpy(K1, a, K0):
"""Convert a GMPY ``mpz`` object to ``dtype``. """
return None
def from_QQ_gmpy(K1, a, K0):
"""Convert a GMPY ``mpq`` object to ``dtype``. """
return None
def from_RealField(K1, a, K0):
"""Convert a real element object to ``dtype``. """
return None
def from_ComplexField(K1, a, K0):
"""Convert a complex element to ``dtype``. """
return None
def from_AlgebraicField(K1, a, K0):
"""Convert an algebraic number to ``dtype``. """
return None
def from_PolynomialRing(K1, a, K0):
"""Convert a polynomial to ``dtype``. """
if a.is_ground:
return K1.convert(a.LC, K0.dom)
def from_FractionField(K1, a, K0):
"""Convert a rational function to ``dtype``. """
return None
def from_MonogenicFiniteExtension(K1, a, K0):
"""Convert an ``ExtensionElement`` to ``dtype``. """
return K1.convert_from(a.rep, K0.ring)
def from_ExpressionDomain(K1, a, K0):
"""Convert a ``EX`` object to ``dtype``. """
return K1.from_sympy(a.ex)
def from_ExpressionRawDomain(K1, a, K0):
"""Convert a ``EX`` object to ``dtype``. """
return K1.from_sympy(a)
def from_GlobalPolynomialRing(K1, a, K0):
"""Convert a polynomial to ``dtype``. """
if a.degree() <= 0:
return K1.convert(a.LC(), K0.dom)
def from_GeneralizedPolynomialRing(K1, a, K0):
return K1.from_FractionField(a, K0)
def unify_with_symbols(K0, K1, symbols):
if (K0.is_Composite and (set(K0.symbols) & set(symbols))) or (K1.is_Composite and (set(K1.symbols) & set(symbols))):
raise UnificationFailed("Cannot unify %s with %s, given %s generators" % (K0, K1, tuple(symbols)))
return K0.unify(K1)
def unify(K0, K1, symbols=None):
"""
Construct a minimal domain that contains elements of ``K0`` and ``K1``.
Known domains (from smallest to largest):
- ``GF(p)``
- ``ZZ``
- ``QQ``
- ``RR(prec, tol)``
- ``CC(prec, tol)``
- ``ALG(a, b, c)``
- ``K[x, y, z]``
- ``K(x, y, z)``
- ``EX``
"""
if symbols is not None:
return K0.unify_with_symbols(K1, symbols)
if K0 == K1:
return K0
if K0.is_EXRAW:
return K0
if K1.is_EXRAW:
return K1
if K0.is_EX:
return K0
if K1.is_EX:
return K1
if K0.is_FiniteExtension or K1.is_FiniteExtension:
if K1.is_FiniteExtension:
K0, K1 = K1, K0
if K1.is_FiniteExtension:
# Unifying two extensions.
# Try to ensure that K0.unify(K1) == K1.unify(K0)
if list(ordered([K0.modulus, K1.modulus]))[1] == K0.modulus:
K0, K1 = K1, K0
return K1.set_domain(K0)
else:
# Drop the generator from other and unify with the base domain
K1 = K1.drop(K0.symbol)
K1 = K0.domain.unify(K1)
return K0.set_domain(K1)
if K0.is_Composite or K1.is_Composite:
K0_ground = K0.dom if K0.is_Composite else K0
K1_ground = K1.dom if K1.is_Composite else K1
K0_symbols = K0.symbols if K0.is_Composite else ()
K1_symbols = K1.symbols if K1.is_Composite else ()
domain = K0_ground.unify(K1_ground)
symbols = _unify_gens(K0_symbols, K1_symbols)
order = K0.order if K0.is_Composite else K1.order
if ((K0.is_FractionField and K1.is_PolynomialRing or
K1.is_FractionField and K0.is_PolynomialRing) and
(not K0_ground.is_Field or not K1_ground.is_Field) and domain.is_Field
and domain.has_assoc_Ring):
domain = domain.get_ring()
if K0.is_Composite and (not K1.is_Composite or K0.is_FractionField or K1.is_PolynomialRing):
cls = K0.__class__
else:
cls = K1.__class__
from sympy.polys.domains.old_polynomialring import GlobalPolynomialRing
if cls == GlobalPolynomialRing:
return cls(domain, symbols)
return cls(domain, symbols, order)
def mkinexact(cls, K0, K1):
prec = max(K0.precision, K1.precision)
tol = max(K0.tolerance, K1.tolerance)
return cls(prec=prec, tol=tol)
if K1.is_ComplexField:
K0, K1 = K1, K0
if K0.is_ComplexField:
if K1.is_ComplexField or K1.is_RealField:
return mkinexact(K0.__class__, K0, K1)
else:
return K0
if K1.is_RealField:
K0, K1 = K1, K0
if K0.is_RealField:
if K1.is_RealField:
return mkinexact(K0.__class__, K0, K1)
elif K1.is_GaussianRing or K1.is_GaussianField:
from sympy.polys.domains.complexfield import ComplexField
return ComplexField(prec=K0.precision, tol=K0.tolerance)
else:
return K0
if K1.is_AlgebraicField:
K0, K1 = K1, K0
if K0.is_AlgebraicField:
if K1.is_GaussianRing:
K1 = K1.get_field()
if K1.is_GaussianField:
K1 = K1.as_AlgebraicField()
if K1.is_AlgebraicField:
return K0.__class__(K0.dom.unify(K1.dom), *_unify_gens(K0.orig_ext, K1.orig_ext))
else:
return K0
if K0.is_GaussianField:
return K0
if K1.is_GaussianField:
return K1
if K0.is_GaussianRing:
if K1.is_RationalField:
K0 = K0.get_field()
return K0
if K1.is_GaussianRing:
if K0.is_RationalField:
K1 = K1.get_field()
return K1
if K0.is_RationalField:
return K0
if K1.is_RationalField:
return K1
if K0.is_IntegerRing:
return K0
if K1.is_IntegerRing:
return K1
if K0.is_FiniteField and K1.is_FiniteField:
return K0.__class__(max(K0.mod, K1.mod, key=default_sort_key))
from sympy.polys.domains import EX
return EX
def __eq__(self, other):
"""Returns ``True`` if two domains are equivalent. """
return isinstance(other, Domain) and self.dtype == other.dtype
def __ne__(self, other):
"""Returns ``False`` if two domains are equivalent. """
return not self == other
def map(self, seq):
"""Rersively apply ``self`` to all elements of ``seq``. """
result = []
for elt in seq:
if isinstance(elt, list):
result.append(self.map(elt))
else:
result.append(self(elt))
return result
def get_ring(self):
"""Returns a ring associated with ``self``. """
raise DomainError('there is no ring associated with %s' % self)
def get_field(self):
"""Returns a field associated with ``self``. """
raise DomainError('there is no field associated with %s' % self)
def get_exact(self):
"""Returns an exact domain associated with ``self``. """
return self
def __getitem__(self, symbols):
"""The mathematical way to make a polynomial ring. """
if hasattr(symbols, '__iter__'):
return self.poly_ring(*symbols)
else:
return self.poly_ring(symbols)
def poly_ring(self, *symbols, order=lex):
"""Returns a polynomial ring, i.e. `K[X]`. """
from sympy.polys.domains.polynomialring import PolynomialRing
return PolynomialRing(self, symbols, order)
def frac_field(self, *symbols, order=lex):
"""Returns a fraction field, i.e. `K(X)`. """
from sympy.polys.domains.fractionfield import FractionField
return FractionField(self, symbols, order)
def old_poly_ring(self, *symbols, **kwargs):
"""Returns a polynomial ring, i.e. `K[X]`. """
from sympy.polys.domains.old_polynomialring import PolynomialRing
return PolynomialRing(self, *symbols, **kwargs)
def old_frac_field(self, *symbols, **kwargs):
"""Returns a fraction field, i.e. `K(X)`. """
from sympy.polys.domains.old_fractionfield import FractionField
return FractionField(self, *symbols, **kwargs)
def algebraic_field(self, *extension, alias=None):
r"""Returns an algebraic field, i.e. `K(\alpha, \ldots)`. """
raise DomainError("Cannot create algebraic field over %s" % self)
def alg_field_from_poly(self, poly, alias=None, root_index=-1):
r"""
Convenience method to construct an algebraic extension on a root of a
polynomial, chosen by root index.
Parameters
==========
poly : :py:class:`~.Poly`
The polynomial whose root generates the extension.
alias : str, optional (default=None)
Symbol name for the generator of the extension.
E.g. "alpha" or "theta".
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 most natural choice in the common cases of
quadratic and cyclotomic fields (the square root on the positive
real or imaginary axis, resp. $\mathrm{e}^{2\pi i/n}$).
Examples
========
>>> from sympy import QQ, Poly
>>> from sympy.abc import x
>>> f = Poly(x**2 - 2)
>>> K = QQ.alg_field_from_poly(f)
>>> K.ext.minpoly == f
True
>>> g = Poly(8*x**3 - 6*x - 1)
>>> L = QQ.alg_field_from_poly(g, "alpha")
>>> L.ext.minpoly == g
True
>>> L.to_sympy(L([1, 1, 1]))
alpha**2 + alpha + 1
"""
from sympy.polys.rootoftools import CRootOf
root = CRootOf(poly, root_index)
alpha = AlgebraicNumber(root, alias=alias)
return self.algebraic_field(alpha, alias=alias)
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)
def inject(self, *symbols):
"""Inject generators into this domain. """
raise NotImplementedError
def drop(self, *symbols):
"""Drop generators from this domain. """
if self.is_Simple:
return self
raise NotImplementedError # pragma: no cover
def is_zero(self, a):
"""Returns True if ``a`` is zero. """
return not a
def is_one(self, a):
"""Returns True if ``a`` is one. """
return a == self.one
def is_positive(self, a):
"""Returns True if ``a`` is positive. """
return a > 0
def is_negative(self, a):
"""Returns True if ``a`` is negative. """
return a < 0
def is_nonpositive(self, a):
"""Returns True if ``a`` is non-positive. """
return a <= 0
def is_nonnegative(self, a):
"""Returns True if ``a`` is non-negative. """
return a >= 0
def canonical_unit(self, a):
if self.is_negative(a):
return -self.one
else:
return self.one
def abs(self, a):
"""Absolute value of ``a``, implies ``__abs__``. """
return abs(a)
def neg(self, a):
"""Returns ``a`` negated, implies ``__neg__``. """
return -a
def pos(self, a):
"""Returns ``a`` positive, implies ``__pos__``. """
return +a
def add(self, a, b):
"""Sum of ``a`` and ``b``, implies ``__add__``. """
return a + b
def sub(self, a, b):
"""Difference of ``a`` and ``b``, implies ``__sub__``. """
return a - b
def mul(self, a, b):
"""Product of ``a`` and ``b``, implies ``__mul__``. """
return a * b
def pow(self, a, b):
"""Raise ``a`` to power ``b``, implies ``__pow__``. """
return a ** b
def exquo(self, a, b):
"""Exact quotient of *a* and *b*. Analogue of ``a / b``.
Explanation
===========
This is essentially the same as ``a / b`` except that an error will be
raised if the division is inexact (if there is any remainder) and the
result will always be a domain element. When working in a
:py:class:`~.Domain` that is not a :py:class:`~.Field` (e.g. :ref:`ZZ`
or :ref:`K[x]`) ``exquo`` should be used instead of ``/``.
The key invariant is that if ``q = K.exquo(a, b)`` (and ``exquo`` does
not raise an exception) then ``a == b*q``.
Examples
========
We can use ``K.exquo`` instead of ``/`` for exact division.
>>> from sympy import ZZ
>>> ZZ.exquo(ZZ(4), ZZ(2))
2
>>> ZZ.exquo(ZZ(5), ZZ(2))
Traceback (most recent call last):
...
ExactQuotientFailed: 2 does not divide 5 in ZZ
Over a :py:class:`~.Field` such as :ref:`QQ`, division (with nonzero
divisor) is always exact so in that case ``/`` can be used instead of
:py:meth:`~.Domain.exquo`.
>>> from sympy import QQ
>>> QQ.exquo(QQ(5), QQ(2))
5/2
>>> QQ(5) / QQ(2)
5/2
Parameters
==========
a: domain element
The dividend
b: domain element
The divisor
Returns
=======
q: domain element
The exact quotient
Raises
======
ExactQuotientFailed: if exact division is not possible.
ZeroDivisionError: when the divisor is zero.
See also
========
quo: Analogue of ``a // b``
rem: Analogue of ``a % b``
div: Analogue of ``divmod(a, b)``
Notes
=====
Since the default :py:attr:`~.Domain.dtype` for :ref:`ZZ` is ``int``
(or ``mpz``) division as ``a / b`` should not be used as it would give
a ``float``.
>>> ZZ(4) / ZZ(2)
2.0
>>> ZZ(5) / ZZ(2)
2.5
Using ``/`` with :ref:`ZZ` will lead to incorrect results so
:py:meth:`~.Domain.exquo` should be used instead.
"""
raise NotImplementedError
def quo(self, a, b):
"""Quotient of *a* and *b*. Analogue of ``a // b``.
``K.quo(a, b)`` is equivalent to ``K.div(a, b)[0]``. See
:py:meth:`~.Domain.div` for more explanation.
See also
========
rem: Analogue of ``a % b``
div: Analogue of ``divmod(a, b)``
exquo: Analogue of ``a / b``
"""
raise NotImplementedError
def rem(self, a, b):
"""Modulo division of *a* and *b*. Analogue of ``a % b``.
``K.rem(a, b)`` is equivalent to ``K.div(a, b)[1]``. See
:py:meth:`~.Domain.div` for more explanation.
See also
========
quo: Analogue of ``a // b``
div: Analogue of ``divmod(a, b)``
exquo: Analogue of ``a / b``
"""
raise NotImplementedError
def div(self, a, b):
"""Quotient and remainder for *a* and *b*. Analogue of ``divmod(a, b)``
Explanation
===========
This is essentially the same as ``divmod(a, b)`` except that is more
consistent when working over some :py:class:`~.Field` domains such as
:ref:`QQ`. When working over an arbitrary :py:class:`~.Domain` the
:py:meth:`~.Domain.div` method should be used instead of ``divmod``.
The key invariant is that if ``q, r = K.div(a, b)`` then
``a == b*q + r``.
The result of ``K.div(a, b)`` is the same as the tuple
``(K.quo(a, b), K.rem(a, b))`` except that if both quotient and
remainder are needed then it is more efficient to use
:py:meth:`~.Domain.div`.
Examples
========
We can use ``K.div`` instead of ``divmod`` for floor division and
remainder.
>>> from sympy import ZZ, QQ
>>> ZZ.div(ZZ(5), ZZ(2))
(2, 1)
If ``K`` is a :py:class:`~.Field` then the division is always exact
with a remainder of :py:attr:`~.Domain.zero`.
>>> QQ.div(QQ(5), QQ(2))
(5/2, 0)
Parameters
==========
a: domain element
The dividend
b: domain element
The divisor
Returns
=======
(q, r): tuple of domain elements
The quotient and remainder
Raises
======
ZeroDivisionError: when the divisor is zero.
See also
========
quo: Analogue of ``a // b``
rem: Analogue of ``a % b``
exquo: Analogue of ``a / b``
Notes
=====
If ``gmpy`` is installed then the ``gmpy.mpq`` type will be used as
the :py:attr:`~.Domain.dtype` for :ref:`QQ`. The ``gmpy.mpq`` type
defines ``divmod`` in a way that is undesirable so
:py:meth:`~.Domain.div` should be used instead of ``divmod``.
>>> a = QQ(1)
>>> b = QQ(3, 2)
>>> a # doctest: +SKIP
mpq(1,1)
>>> b # doctest: +SKIP
mpq(3,2)
>>> divmod(a, b) # doctest: +SKIP
(mpz(0), mpq(1,1))
>>> QQ.div(a, b) # doctest: +SKIP
(mpq(2,3), mpq(0,1))
Using ``//`` or ``%`` with :ref:`QQ` will lead to incorrect results so
:py:meth:`~.Domain.div` should be used instead.
"""
raise NotImplementedError
def invert(self, a, b):
"""Returns inversion of ``a mod b``, implies something. """
raise NotImplementedError
def revert(self, a):
"""Returns ``a**(-1)`` if possible. """
raise NotImplementedError
def numer(self, a):
"""Returns numerator of ``a``. """
raise NotImplementedError
def denom(self, a):
"""Returns denominator of ``a``. """
raise NotImplementedError
def half_gcdex(self, a, b):
"""Half extended GCD of ``a`` and ``b``. """
s, t, h = self.gcdex(a, b)
return s, h
def gcdex(self, a, b):
"""Extended GCD of ``a`` and ``b``. """
raise NotImplementedError
def cofactors(self, a, b):
"""Returns GCD and cofactors of ``a`` and ``b``. """
gcd = self.gcd(a, b)
cfa = self.quo(a, gcd)
cfb = self.quo(b, gcd)
return gcd, cfa, cfb
def gcd(self, a, b):
"""Returns GCD of ``a`` and ``b``. """
raise NotImplementedError
def lcm(self, a, b):
"""Returns LCM of ``a`` and ``b``. """
raise NotImplementedError
def log(self, a, b):
"""Returns b-base logarithm of ``a``. """
raise NotImplementedError
def sqrt(self, a):
"""Returns square root of ``a``. """
raise NotImplementedError
def evalf(self, a, prec=None, **options):
"""Returns numerical approximation of ``a``. """
return self.to_sympy(a).evalf(prec, **options)
n = evalf
def real(self, a):
return a
def imag(self, a):
return self.zero
def almosteq(self, a, b, tolerance=None):
"""Check if ``a`` and ``b`` are almost equal. """
return a == b
def characteristic(self):
"""Return the characteristic of this domain. """
raise NotImplementedError('characteristic()')
__all__ = ['Domain']