first step towards removal of IntegralDomain

Author: fchapoton

src/sage/categories/integral_domains.py

@@ -143,6 +143,38 @@ def is_integral_domain(self, proof=True):
             """
             return True
 
+        def is_field(self, proof=True):
+            r"""
+            Return ``True`` if this ring is a field.
+
+            EXAMPLES::
+
+                sage: ZZ['x'].is_field()
+                False
+            """
+            if self.is_finite():
+                return True
+            if proof:
+                raise NotImplementedError("unable to determine whether or not is a field.")
+            else:
+                return False
+
+        def localization(self, additional_units, names=None, normalize=True, category=None):
+            """
+            Return the localization of ``self`` at the given additional units.
+
+            EXAMPLES::
+
+                sage: R.<x, y> = GF(3)[]
+                sage: R.localization((x*y, x**2 + y**2))                                    # needs sage.rings.finite_rings
+                Multivariate Polynomial Ring in x, y over Finite Field of size 3
+                 localized at (y, x, x^2 + y^2)
+                sage: ~y in _                                                               # needs sage.rings.finite_rings
+                True
+            """
+            from sage.rings.localization import Localization
+            return Localization(self, additional_units, names=names, normalize=normalize, category=category)
+
         def _test_fraction_field(self, **options):
             r"""
             Test that the fraction field, if it is implemented, works

src/sage/categories/rings.py

@@ -554,6 +554,22 @@ def is_subring(self, other):
             except (TypeError, AttributeError):
                 return False
 
+        def localization(self, *args, **kwds):
+            """
+            Return the localization of ``self``.
+
+            This only works for integral domains.
+
+            EXAMPLES::
+
+                sage: R = Zmod(6)
+                sage: R.localization((4))
+                Traceback (most recent call last):
+                ...
+                TypeError: self must be an integral domain
+            """
+            raise TypeError("self must be an integral domain")
+
         def bracket(self, x, y):
             """
             Return the Lie bracket `[x, y] = x y - y x` of `x` and `y`.

src/sage/rings/abc.pyx

@@ -1,9 +1,6 @@
 """
 Abstract base classes for rings
 """
-from sage.rings.ring import IntegralDomain
-
-
 class NumberField_quadratic(Field):
     r"""
     Abstract base class for :class:`~sage.rings.number_field.number_field.NumberField_quadratic`.
@@ -419,7 +416,7 @@ class Order:
     pass
 
 
-class pAdicRing(IntegralDomain):
+class pAdicRing(CommutativeRing):
     r"""
     Abstract base class for :class:`~sage.rings.padics.generic_nodes.pAdicRingGeneric`.
 

src/sage/rings/localization.py

@@ -180,7 +180,7 @@
 
 from sage.structure.unique_representation import UniqueRepresentation
 from sage.categories.integral_domains import IntegralDomains
-from sage.rings.ring import IntegralDomain
+from sage.structure.parent import Parent
 from sage.structure.element import IntegralDomainElement
 
 
@@ -193,7 +193,7 @@ def normalize_extra_units(base_ring, add_units, warning=True):
 
     INPUT:
 
-    - ``base_ring`` -- an instance of :class:`IntegralDomain`
+    - ``base_ring`` -- a ring in the category of :class:`IntegralDomains`
     - ``add_units`` -- list of elements from base ring
     - ``warning`` -- boolean (default: ``True``); to suppress a warning which
       is thrown if no normalization was possible
@@ -561,7 +561,7 @@ def _integer_(self, Z=None):
         return self._value._integer_(Z=Z)
 
 
-class Localization(IntegralDomain, UniqueRepresentation):
+class Localization(Parent, UniqueRepresentation):
     r"""
     The localization generalizes the construction of the field of fractions of
     an integral domain to an arbitrary ring. Given a (not necessarily
@@ -580,21 +580,18 @@ class Localization(IntegralDomain, UniqueRepresentation):
     this class relies on the construction of the field of fraction and is
     therefore restricted to integral domains.
 
-    Accordingly, this class is inherited from :class:`IntegralDomain` and can
-    only be used in that context. Furthermore, the base ring should support
+    Accordingly, the base ring must be in the category of ``IntegralDomains``.
+    Furthermore, the base ring should support
     :meth:`sage.structure.element.CommutativeRingElement.divides` and the exact
     division operator ``//`` (:meth:`sage.structure.element.Element.__floordiv__`)
     in order to guarantee a successful application.
 
     INPUT:
 
-    - ``base_ring`` -- an instance of :class:`Ring` allowing the construction
-      of :meth:`fraction_field` (that is an integral domain)
+    - ``base_ring`` -- a ring in the category of ``IntegralDomains``
     - ``extra_units`` -- tuple of elements of ``base_ring`` which should be
       turned into units
-    - ``names`` -- passed to :class:`IntegralDomain`
-    - ``normalize`` -- boolean (default: ``True``); passed to :class:`IntegralDomain`
-    - ``category`` -- (default: ``None``) passed to :class:`IntegralDomain`
+    - ``category`` -- (default: ``None``) passed to :class:`Parent`
     - ``warning`` -- boolean (default: ``True``); to suppress a warning which
       is thrown if ``self`` cannot be represented uniquely
 
@@ -712,7 +709,7 @@ def __init__(self, base_ring, extra_units, names=None, normalize=True, category=
             # since by construction the base ring must contain non units self must be infinite
             category = IntegralDomains().Infinite()
 
-        IntegralDomain.__init__(self, base_ring, names=names, normalize=normalize, category=category)
+        Parent.__init__(self, base=base_ring, names=names, normalize=normalize, category=category)
         self._extra_units = tuple(extra_units)
         self._fraction_field = base_ring.fraction_field()
         self._populate_coercion_lists_()

src/sage/rings/number_field/number_field_base.pyx

@@ -65,7 +65,7 @@ cdef class NumberField(Field):
         +Infinity
     """
     # This token docstring is mostly there to prevent Sphinx from pasting in
-    # the docstring of the __init__ method inherited from IntegralDomain, which
+    # the docstring of the __init__ method inherited from Field, which
     # is rather confusing.
     def _pushout_(self, other):
         r"""

src/sage/rings/power_series_ring.py

@@ -1323,7 +1323,9 @@ def laurent_series_ring(self):
             return self.__laurent_series_ring
 
 
-class PowerSeriesRing_domain(PowerSeriesRing_generic, ring.IntegralDomain):
+class PowerSeriesRing_domain(PowerSeriesRing_generic):
+    _default_category = _IntegralDomains
+
     def fraction_field(self):
         """
         Return the Laurent series ring over the fraction field of the base

src/sage/rings/ring.pyx

@@ -773,25 +773,6 @@ cdef class CommutativeRing(Ring):
         Ring.__init__(self, base_ring, names=names, normalize=normalize,
                       category=category)
 
-    def localization(self, additional_units, names=None, normalize=True, category=None):
-        """
-        Return the localization of ``self`` at the given additional units.
-
-        EXAMPLES::
-
-            sage: R.<x, y> = GF(3)[]
-            sage: R.localization((x*y, x**2 + y**2))                                    # needs sage.rings.finite_rings
-            Multivariate Polynomial Ring in x, y over Finite Field of size 3
-             localized at (y, x, x^2 + y^2)
-            sage: ~y in _                                                               # needs sage.rings.finite_rings
-            True
-        """
-        if not self.is_integral_domain():
-            raise TypeError("self must be an integral domain.")
-
-        from sage.rings.localization import Localization
-        return Localization(self, additional_units, names=names, normalize=normalize, category=category)
-
     def fraction_field(self):
         """
         Return the fraction field of ``self``.
@@ -1018,29 +999,6 @@ cdef class IntegralDomain(CommutativeRing):
         CommutativeRing.__init__(self, base_ring, names=names, normalize=normalize,
                                  category=category)
 
-    def is_field(self, proof=True):
-        r"""
-        Return ``True`` if this ring is a field.
-
-        EXAMPLES::
-
-            sage: GF(7).is_field()
-            True
-
-        The following examples have their own ``is_field`` implementations::
-
-            sage: ZZ.is_field(); QQ.is_field()
-            False
-            True
-            sage: R.<x> = PolynomialRing(QQ); R.is_field()
-            False
-        """
-        if self.is_finite():
-            return True
-        if proof:
-            raise NotImplementedError("unable to determine whether or not is a field.")
-        else:
-            return False
 
 cdef class NoetherianRing(CommutativeRing):
     _default_category = NoetherianRings()