Ticket #13510: trac_13510.patch

sage/graphs/graph.py

@@ -2137 +2137 @@
 
         # these values are possibly the infinity !!!!
 
-        start_self = start(start_self) if start_self <= self.order() else self.order()+2 
+        start_self = start(start_self) if start_self <= self.order() else self.order()+2
         start_complement = start(start_complement) if start_complement <= self.order() else self.order()+2
-            
+
         counter_example = None
 
         for i in range(min(start_self, start_complement), self.order()+1,2):
@@ -2147 +2147 @@
             # trying in self
             if i >= start_self:
                 counter_example = self.subgraph_search(graphs.CycleGraph(i), induced = True)
-                
+
                 if counter_example is not None:
                     break
 
@@ -2163 +2163 @@
         else:
             return counter_example is None
 
-    def is_strongly_regular(self, return_parameters=False):
+    def is_strongly_regular(self, parameters=False):
         r"""
         Tests whether ``self`` is strongly regular.
 
-        A graph `G` is said to be strongly regular with parameters `(k, \lambda,
-        \mu)` if and only if:
-
-            * `G` is `k`-regular
+        A graph `G` is said to be strongly regular with parameters (n, k,
+        \lambda, \mu)` if and only if:
+
+            * `G` has `n` vertices.
+
+            * `G` is `k`-regular.
 
             * Any two adjacent vertices of `G` have `\lambda` common neighbors.
 
@@ -2178 +2180 @@
 
         INPUT:
 
-        - ``return_parameters`` (boolean) -- whether to return the triple
-          `(k,\lambda,\mu)`. If ``return_parameters = False`` (default), this
-          method only returns ``True`` and ``False`` answers. If
-          ``return_parameters=True``, the ``True`` answers are replaced by
-          triples `(k,\lambda,\mu)`. See definition above.
+        - ``parameters`` (boolean) -- whether to return the quadruple `(n,
+          k,\lambda,\mu)`. If ``parameters = False`` (default), this method only
+          returns ``True`` and ``False`` answers. If ``parameters=True``, the
+          ``True`` answers are replaced by quadruples `(n, k,\lambda,\mu)`. See
+          definition above.
 
         EXAMPLES:
 
@@ -2191 +2193 @@
             sage: g = graphs.PetersenGraph()
             sage: g.is_strongly_regular()
             True
-            sage: g.is_strongly_regular(return_parameters = True)
-            (3, 0, 1)
+            sage: g.is_strongly_regular(parameters = True)
+            (10, 3, 0, 1)
 
         And Clebsch's graph is too::
 
             sage: g = graphs.ClebschGraph()
             sage: g.is_strongly_regular()
             True
-            sage: g.is_strongly_regular(return_parameters = True)
-            (5, 0, 2)
+            sage: g.is_strongly_regular(parameters = True)
+            (16, 5, 0, 2)
 
         But Chvatal's graph is not::
 
@@ -2242 +2244 @@
                             if m != inter:
                                 return False
 
-            if return_parameters:
-                return (k,l,m)
+            if parameters:
+                return (self.order(),k,l,m)
             else:
                 return True
 

sage/graphs/graph_coloring.py

@@ -225 +225 @@
     """
     #Take care of the stupid stuff
     if n == 1:
-        return int(len(G.edges()) == 0)
+        return int(G.size() == 0)
     if n < 1:
         if n == 0:
-            return int(len(G.vertices()) == 0)
+            return int(G.order() == 0)
         else:
             #negative colors?? what does that even mean?
             return 0
@@ -272 +272 @@
     o = G.order()
     if o == 0:
         return 0
-    if len(G.edges()) == 0:
+    if G.size() == 0:
         return 1
     elif G.is_bipartite(): #can we do it in linear time?
         return 2

sage/graphs/spanning_tree.pyx

@@ -6 +6 @@
 [JoynerNguyenCohen2010]_ for descriptions of spanning tree algorithms,
 including minimum spanning trees.
 
+.. SEEALSO::
+
+   * :meth:`GenericGraph.min_spanning_tree
+     <sage.graphs.generic_graph.GenericGraph.min_spanning_tree>`.
+
 **Todo**
 
 * Rewrite :func:`kruskal` to use priority queues. Once Cython has support