From 9961827878ce50fe6add58b38282befa1165a795 Mon Sep 17 00:00:00 2001
From: Matthew Henderson <matthew.james.henderson@gmail.com>
Date: Wed, 27 Nov 2024 09:34:26 +0000
Subject: [PATCH 1/2] Implement edge list-colouring.

---
 src/vizing/__init__.py            | 26 ++++++++++++++++++++++++++
 tests/test_edge-list-colouring.py | 20 ++++++++++++++++++++
 2 files changed, 46 insertions(+)
 create mode 100644 tests/test_edge-list-colouring.py

diff --git a/src/vizing/__init__.py b/src/vizing/__init__.py
index 2b88da3..a6c696c 100644
--- a/src/vizing/__init__.py
+++ b/src/vizing/__init__.py
@@ -27,3 +27,29 @@ def node_list_colouring_solution(G):
     G.nodes[node]['colour'] = S[node]
   return(G)
 
+def edge_list_colouring_problem(G):
+  """
+  Return a constraint problem representing an edge list-colouring instance.
+
+  :param G: A graph with lists of permissible colours assigned to edges.
+  :return An edge list-colouring constraint problem.
+  """
+  P = constraint.Problem()
+  for edge in G.edges():
+    P.addVariable(edge, G.edges[edge]['permissible'])
+  for node in G.nodes():
+    P.addConstraint(constraint.AllDifferentConstraint(), [tuple(sorted(x)) for x in G.edges(node)])
+  return(P)
+
+def edge_list_colouring_solution(G):
+  """
+  Return an edge-coloured graph.
+
+  :param G: A graph with lists of permissible colours assigned to edges.
+  :return A properly edge list-coloured graph.
+  """
+  P = edge_list_colouring_problem(G)
+  S = P.getSolution()
+  for edge in G.edges():
+    G.edges()[edge]['colour'] = S[edge]
+  return(G)
diff --git a/tests/test_edge-list-colouring.py b/tests/test_edge-list-colouring.py
new file mode 100644
index 0000000..f129a3e
--- /dev/null
+++ b/tests/test_edge-list-colouring.py
@@ -0,0 +1,20 @@
+import networkx as nx
+import vizing as vz
+
+def test_edge_list_colouring_problem():
+  G = nx.complete_graph(3)
+  permissible_dict_edge = {(0, 1): [0, 1], (0, 2): [1, 2], (1, 2): [2, 4]}
+  nx.set_edge_attributes(G, permissible_dict_edge, "permissible")
+  nx.set_edge_attributes(G, None, "colour")
+  P = vz.edge_list_colouring_problem(G)
+  assert P._variables == {(0, 1): [0, 1], (0, 2): [1, 2], (1, 2): [2, 4]}
+
+def test_edge_list_colouring_solution():
+  G = nx.complete_graph(3)
+  permissible_dict_edge = {(0, 1): [0, 1], (0, 2): [1, 2], (1, 2): [2, 4]}
+  nx.set_edge_attributes(G, permissible_dict_edge, "permissible")
+  nx.set_edge_attributes(G, None, "colour")
+  G = vz.edge_list_colouring_solution(G)
+  assert G.edges()[(0, 1)]['colour'] == 1
+  assert G.edges()[(0, 2)]['colour'] == 2
+  assert G.edges()[(1, 2)]['colour'] == 4

From ba6f6adb0005fab5fea30a594f4e439091bdbeff Mon Sep 17 00:00:00 2001
From: Matthew Henderson <matthew.james.henderson@gmail.com>
Date: Wed, 27 Nov 2024 09:34:51 +0000
Subject: [PATCH 2/2] Bump development version number: 0.1.0.9000 ->
 0.1.0.9001.

---
 pyproject.toml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pyproject.toml b/pyproject.toml
index 3c61db9..3c9a59a 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "vizing"
-version = "0.1.0.9000"
+version = "0.1.0.9001"
 description = "Constraint-based list-colouring in Python."
 authors = ["Matthew Henderson <matthew.james.henderson@gmail.com>"]
 readme = "README.md"