From f9efd6ed614aa0eb66101b158594de506ce2c417 Mon Sep 17 00:00:00 2001
From: "Robert L. Miller" <rlm@rlmiller.org>
Date: Fri, 20 Feb 2009 18:41:53 -0800
Subject: [PATCH] Don't use symbolic variables for graph plotting

---
 src/sage/graphs/graph.py      |  6 ++++++
 src/sage/graphs/graph_plot.py | 12 +++++-------
 2 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/src/sage/graphs/graph.py b/src/sage/graphs/graph.py
index 16f81b0ed5b..2cbce4e05d2 100644
--- a/src/sage/graphs/graph.py
+++ b/src/sage/graphs/graph.py
@@ -5863,6 +5863,12 @@ def plot(self, **options):
             sage: g.add_edges([(0,0,'a'),(0,0,'b'),(0,1,'c'),(0,1,'d'),
             ...     (0,1,'e'),(0,1,'f'),(0,1,'f'),(2,1,'g'),(2,2,'h')])
             sage: g.plot(edge_labels=True, color_by_label=True, edge_style='dashed')
+
+            sage: S = SupersingularModule(389)
+            sage: H = S.hecke_matrix(2)
+            sage: D = DiGraph(H)
+            sage: P = D.plot()
+
         """
         from sage.graphs.graph_plot import GraphPlot
         return GraphPlot(graph=self, options=options).plot()
diff --git a/src/sage/graphs/graph_plot.py b/src/sage/graphs/graph_plot.py
index 71674749701..82dc668b7b4 100644
--- a/src/sage/graphs/graph_plot.py
+++ b/src/sage/graphs/graph_plot.py
@@ -431,8 +431,6 @@ def set_edges(self, **edge_options):
                 elif len(edges_to_draw[(a,b)]) > 1:
                     # Multi-edge
                     local_labels = edges_to_draw.pop((a,b))
-                    x = SymbolicVariable('x')
-                    d = SymbolicVariable('d')
 
                     # Compute perpendicular bisector
                     p1 = self._pos[a]
@@ -440,12 +438,12 @@ def set_edges(self, **edge_options):
                     M = ((p1[0]+p2[0])/2, (p1[1]+p2[1])/2) # midpoint
                     if not p1[1] == p2[1]:
                         S = (p1[0]-p2[0])/(p2[1]-p1[1]) # perp slope
-                        y = S*x-S*M[0]+M[1] # perp bisector line
+                        y = lambda x : S*x-S*M[0]+M[1] # perp bisector line
 
                         # f,g are functions of distance d to determine x values
                         # on line y at d from point M
-                        f = Sqrt(d**2/(1+S**2)) + M[0]
-                        g = -Sqrt(d**2/(1+S**2)) + M[0]
+                        f = lambda d : sqrt(d**2/(1+S**2)) + M[0]
+                        g = lambda d : -sqrt(d**2/(1+S**2)) + M[0]
 
                         odd_x = f
                         even_x = g
@@ -453,8 +451,8 @@ def set_edges(self, **edge_options):
                             odd_y = lambda d : M[1]
                             even_y = odd_y
                         else:
-                            odd_y = y(f)
-                            even_y = y(g)
+                            odd_y = lambda x : y(f(x))
+                            even_y = lambda x : y(g(x))
                     else:
                         odd_x = lambda d : M[0]
                         even_x = odd_x