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Fix AttributeError in PowerSeriesRing for division #39713

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Fix AttributeError in PowerSeriesRing for division #39713

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b0c1bf6
Add __truediv__ for base ring unit division
vidipsingh Mar 15, 2025
9244774
Add _pseudo_fraction_field to PowerSeriesRing_generic
vidipsingh Mar 17, 2025
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24 changes: 21 additions & 3 deletions src/sage/rings/power_series_ring.py
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Original file line number Diff line number Diff line change
Expand Up @@ -154,6 +154,7 @@
from sage.structure.parent import Parent
from sage.structure.nonexact import Nonexact
from sage.structure.unique_representation import UniqueRepresentation
from sage.rings.laurent_series_ring import LaurentSeriesRing

_CommutativeRings = commutative_rings.CommutativeRings()
import sage.categories.integral_domains as integral_domains
Expand All @@ -171,8 +172,8 @@
from .laurent_series_ring import LaurentSeriesRing
from .laurent_series_ring_element import LaurentSeries
except ImportError:
LaurentSeriesRing = ()
LaurentSeries = ()
from sage.rings.laurent_series_ring import LaurentSeriesRing
from sage.rings.laurent_series_ring_element import LaurentSeries

lazy_import('sage.rings.lazy_series_ring', 'LazyPowerSeriesRing')

Expand Down Expand Up @@ -602,6 +603,24 @@ def __init__(self, base_ring, name=None, default_prec=None, sparse=False,
else:
self.__generator = self.element_class(self, R.gen(), is_gen=True)

def _pseudo_fraction_field(self):
"""
Return the pseudo-fraction field of this power series ring.

This is the Laurent series ring over the same base ring with the same
variable name, where division is defined.

EXAMPLES::
sage: R.<x> = PowerSeriesRing(QQ)
sage: R._pseudo_fraction_field()
Laurent Series Ring in x over Rational Field
sage: K.<z> = PowerSeriesRing(QQ)
sage: R.<x> = PowerSeriesRing(K)
sage: R._pseudo_fraction_field()
Laurent Series Ring in x over Power Series Ring in z over Rational Field
"""
return LaurentSeriesRing(self.base_ring(), self._names[0])

def variable_names_recursive(self, depth=None):
r"""
Return the list of variable names of this and its base rings.
Expand Down Expand Up @@ -1422,7 +1441,6 @@ def fraction_field(self):
"""
return self.laurent_series_ring()


def unpickle_power_series_ring_v0(base_ring, name, default_prec, sparse):
"""
Unpickle (deserialize) a univariate power series ring according to
Expand Down