trac #15623: Rebase on updated #15622

sagemath · Jan 7, 2014 · 3531566 · 3531566
2 parents dcb8a0b + 6398780
commit 3531566
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Showing 3 changed files with 19 additions and 6 deletions.
diff --git a/src/sage/combinat/posets/hasse_diagram.py b/src/sage/combinat/posets/hasse_diagram.py
@@ -463,9 +463,9 @@ def dual(self):
             sage: H.is_isomorphic( H.dual() )
             False
         """
-        H = HasseDiagram(self.reverse())
+        H = self.reverse()
         H.relabel(perm=range(H.num_verts()-1,-1,-1), inplace=True)
-        return H
+        return HasseDiagram(H)
 
     def interval(self, x, y):
         """

diff --git a/src/sage/graphs/base/static_sparse_backend.pyx b/src/sage/graphs/base/static_sparse_backend.pyx
@@ -467,12 +467,12 @@ class StaticSparseBackend(CGraphBackend):
 
         TEST::
 
-            sage: from sage.graphs.base.static_sparse_backend import StaticSparseCGraph
-            sage: g = StaticSparseCGraph(graphs.PetersenGraph())
+            sage: from sage.graphs.base.static_sparse_backend import StaticSparseBackend
+            sage: g = StaticSparseBackend(graphs.PetersenGraph())
             sage: g.relabel([],True)
             Traceback (most recent call last):
             ...
-            ValueError: Thou shalt not remove a vertex from an immutable graph
+            ValueError: Thou shalt not relabel an immutable graph
 
         """
         raise ValueError("Thou shalt not relabel an immutable graph")

diff --git a/src/sage/graphs/generic_graph.py b/src/sage/graphs/generic_graph.py
@@ -16557,12 +16557,22 @@ def relabel(self, perm=None, inplace=True, return_map=False, check_input = True,
             sage: Graph(graphs.PetersenGraph(), immutable=True).relabel({})
             Traceback (most recent call last):
             ...
-            ValueError: Thou shalt not relabel an immutable graph
+            ValueError: To relabel an immutable graph use inplace=False
+
+        A couple of lines to remove when hasse diagrams will not have a
+        ``._immutable`` attribute by default::
+
+            sage: from sage.combinat.posets.hasse_diagram import HasseDiagram
+            sage: if getattr(HasseDiagram,'_immutable', "YES") == "YES":
+            ....:     print "two lines must be removed from this function"
+
         """
         from sage.groups.perm_gps.permgroup_element import PermutationGroupElement
 
         if not inplace:
             G = self.copy(immutable=False)
+            if getattr(G, "_immutable", False): # can be removed when posets
+                G._immutable = False            # have immutable backends
             perm2 = G.relabel(perm,
                               return_map= return_map,
                               check_input = check_input,
@@ -16576,6 +16586,9 @@ def relabel(self, perm=None, inplace=True, return_map=False, check_input = True,
             else:
                 return G
 
+        if getattr(self, "_immutable", False):
+            raise ValueError("To relabel an immutable graph use inplace=False")
+
         # If perm is not a dictionary, we build one !
 
         if perm is None: