Ticket #3927: sage-trac3927a.patch

a/sage/structure/factorization.py

@@ -828 +828 @@
-            d2 = dict(other)
-            s = {}
-            for a in set(d1.keys()).union(set(d2.keys())):
-
-
-
-
-
+
-            return Factorization(list(s.iteritems()), unit=self.unit()*other.unit())
-        else:
-            return Factorization(list(self) + list(other), unit=self.unit()*other.unit())
@@ -951 +947 @@
-        """
-        return self.value()
-        
+    def gcd(self, other):
+        r"""
+        Return the gcd of two factorizations.
+
+        EXAMPLES:
+            sage: factor(-30).gcd(factor(-160))
+            2 * 5
+            sage: factor(gcd(-30,160))
+            2 * 5
+
+        """
+        if not isinstance(other, Factorization):
+            return self * Factorization([(other, 1)])
+        if self.is_commutative() and other.is_commutative():
+            d1 = dict(self)
+            d2 = dict(other)
+            s = {}
+            for a in set(d1.keys()).intersection(set(d2.keys())):
+                s[a] = min(d1[a],d2[a])
+            return Factorization(list(s.iteritems()), unit=self.base_ring()(1))
+        else:
+            raise NotImplementedError, "gcd is not implemented for non-commutative factorizations"
+
+    def lcm(self, other):
+        r"""
+        Return the lcm of two factorizations.
+
+        EXAMPLES:
+            sage: factor(-10).lcm(factor(-16))
+            2^4 * 5
+            sage: factor(lcm(-10,16))
+            2^4 * 5
+
+        """
+        if not isinstance(other, Factorization):
+            return self * Factorization([(other, 1)])
+        if self.is_commutative() and other.is_commutative():
+            d1 = dict(self)
+            d2 = dict(other)
+            s = {}
+            for a in set(d1.keys()).union(set(d2.keys())):
+                s[a] = max(d1.get(a,0),d2.get(a,0))
+            return Factorization(list(s.iteritems()), unit=self.base_ring()(1))
+        else:
+            raise NotImplementedError, "gcd is not implemented for non-commutative factorizations"
+
-