move is_subring to category

sagemath · Oct 29, 2024 · df30ad5 · df30ad5
1 parent 0314517
commit df30ad5
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Showing 2 changed files with 48 additions and 48 deletions.
diff --git a/src/sage/categories/rings.py b/src/sage/categories/rings.py
@@ -457,6 +457,54 @@ def is_zero(self) -> bool:
             """
             return self.one() == self.zero()
 
+        def is_subring(self, other):
+            """
+            Return ``True`` if the canonical map from ``self`` to ``other`` is
+            injective.
+
+            This raises a :exc:`NotImplementedError` if not known.
+
+            EXAMPLES::
+
+                sage: ZZ.is_subring(QQ)
+                True
+                sage: ZZ.is_subring(GF(19))
+                False
+
+            TESTS::
+
+                sage: QQ.is_subring(QQ['x'])
+                True
+                sage: QQ.is_subring(GF(7))
+                False
+                sage: QQ.is_subring(CyclotomicField(7))                                     # needs sage.rings.number_field
+                True
+                sage: QQ.is_subring(ZZ)
+                False
+
+            Every ring is a subring of itself, :issue:`17287`::
+
+                sage: QQbar.is_subring(QQbar)                                               # needs sage.rings.number_field
+                True
+                sage: RR.is_subring(RR)
+                True
+                sage: CC.is_subring(CC)                                                     # needs sage.rings.real_mpfr
+                True
+                sage: x = polygen(ZZ, 'x')
+                sage: K.<a> = NumberField(x^3 - x + 1/10)                                   # needs sage.rings.number_field
+                sage: K.is_subring(K)                                                       # needs sage.rings.number_field
+                True
+                sage: R.<x> = RR[]
+                sage: R.is_subring(R)
+                True
+            """
+            if self is other:
+                return True
+            try:
+                return self.Hom(other).natural_map().is_injective()
+            except (TypeError, AttributeError):
+                return False
+
         def bracket(self, x, y):
             """
             Return the Lie bracket `[x, y] = x y - y x` of `x` and `y`.

diff --git a/src/sage/rings/ring.pyx b/src/sage/rings/ring.pyx
@@ -652,54 +652,6 @@ cdef class Ring(ParentWithGens):
         """
         return True
 
-    def is_subring(self, other):
-        """
-        Return ``True`` if the canonical map from ``self`` to ``other`` is
-        injective.
-
-        Raises a :exc:`NotImplementedError` if not known.
-
-        EXAMPLES::
-
-            sage: ZZ.is_subring(QQ)
-            True
-            sage: ZZ.is_subring(GF(19))
-            False
-
-        TESTS::
-
-            sage: QQ.is_subring(QQ['x'])
-            True
-            sage: QQ.is_subring(GF(7))
-            False
-            sage: QQ.is_subring(CyclotomicField(7))                                     # needs sage.rings.number_field
-            True
-            sage: QQ.is_subring(ZZ)
-            False
-
-        Every ring is a subring of itself, :issue:`17287`::
-
-            sage: QQbar.is_subring(QQbar)                                               # needs sage.rings.number_field
-            True
-            sage: RR.is_subring(RR)
-            True
-            sage: CC.is_subring(CC)                                                     # needs sage.rings.real_mpfr
-            True
-            sage: x = polygen(ZZ, 'x')
-            sage: K.<a> = NumberField(x^3 - x + 1/10)                                   # needs sage.rings.number_field
-            sage: K.is_subring(K)                                                       # needs sage.rings.number_field
-            True
-            sage: R.<x> = RR[]
-            sage: R.is_subring(R)
-            True
-        """
-        if self is other:
-            return True
-        try:
-            return self.Hom(other).natural_map().is_injective()
-        except (TypeError, AttributeError):
-            return False
-
     def is_prime_field(self):
         r"""
         Return ``True`` if this ring is one of the prime fields `\QQ` or