implement enumerate_boundaries() for CycleDoubleCover

graph_tools/parameters.py

@@ -17,7 +17,7 @@ def _init_():
     SimpleParameterBase, GraphParameterBase
 
   from fractions import Fraction
-  from itertools import chain, combinations
+  from itertools import chain, combinations, product
   from functools import reduce
   from collections import defaultdict
 
@@ -51,6 +51,18 @@ def _init_():
     def is_compatible(self, boundary, e_a, e_b):
       return boundary[e_a] == boundary[e_b]
 
+    def enumerate_boundaries(self, n):
+      tuples = [ (i, j) for j in range(self.k) for i in range(j) ]
+
+      def is_boundary(b):
+        counts = [0] * self.k
+        for i, j in b:
+          counts[i] += 1
+          counts[j] += 1
+        return all( c % 2 == 0 for c in counts )
+
+      return ( b for b in product(tuples, repeat=n) if is_boundary(b) )
+
 
   @OneOfKind
   class EdgeColoring(SimpleParameterBase):