neo4j/graph: Optimize some services of `SequentialNodeCollection`.

[nit.git] / lib / poset.nit

diff --git a/lib/poset.nit b/lib/poset.nit
index 3e9b3fa..a5425dd 100644 (file)
--- a/lib/poset.nit
+++ b/lib/poset.nit
@@ -226,21 +226,26 @@ class POSet[E: Object]
 
        # Write the POSet as a graphviz digraph.
        #
-       # Nodes are identified with their `to_s`.
+       # Nodes are labeled with their `to_s` so homonymous nodes may appear.
        # Edges are unlabeled.
        fun write_dot(f: OStream)
        do
                f.write "digraph \{\n"
+               var ids = new HashMap[E, Int]
+               for x in elements.keys do
+                       ids[x] = ids.length
+               end
                for x in elements.keys do
                        var xstr = x.to_s.escape_to_dot
-                       f.write "\"{xstr}\";\n"
+                       var nx = "n{ids[x]}"
+                       f.write "{nx}[label=\"{xstr}\"];\n"
                        var xe = self.elements[x]
                        for y in xe.dtos do
-                               var ystr = y.to_s.escape_to_dot
+                               var ny = "n{ids[y]}"
                                if self.has_edge(y,x) then
-                                       f.write "\"{xstr}\" -> \"{ystr}\"[dir=both];\n"
+                                       f.write "{nx} -> {ny}[dir=both];\n"
                                else
-                                       f.write "\"{xstr}\" -> \"{ystr}\";\n"
+                                       f.write "{nx} -> {ny};\n"
                                end
                        end
                end