Merge pull request #257 from RazinShaikh/fix-copy

fix multigraph spider copy

pyzx/hrules.py

@@ -97,17 +97,17 @@ def fuse_hboxes(g: BaseGraph[VT,ET], matches: List[ET]) -> rules.RewriteOutputTy
                 etab[upair(v1,n)] = [1,0]
             else:
                 etab[upair(v1,n)] = [0,1]
-    
+
     return (etab, rem_verts, [], True)
 
 
 
-MatchCopyType = Tuple[VT,VT,VertexType,FractionLike,FractionLike,List[VT]]
+MatchCopyType = Tuple[VT,VT,VertexType,FractionLike,FractionLike,List[ET]]
 
 def match_copy(
         g: BaseGraph[VT,ET], 
         vertexf:Optional[Callable[[VT],bool]]=None
-        ) -> List[MatchCopyType[VT]]:
+        ) -> List[MatchCopyType[VT, ET]]:
     """Finds arity-1 spiders (with a 0 or pi phase) that can be copied through their neighbor.""" 
     if vertexf is not None: candidates = set([v for v in g.vertices() if vertexf(v)])
     else: candidates = g.vertex_set()
@@ -159,7 +159,8 @@ def match_copy(
         else:
             continue
         neigh = [n for n in g.neighbors(w) if n != v]
-        m.append((v,w,copy_type,phases[v],phases[w],neigh))
+        neigh_edges = [e for e in g.incident_edges(w) if v not in g.edge_st(e)]
+        m.append((v,w,copy_type,phases[v],phases[w],neigh_edges))
         candidates.discard(w)
         candidates.difference_update(neigh)
         taken.add(w)
@@ -168,36 +169,37 @@ def match_copy(
     return m
 
 def apply_copy(
-        g: BaseGraph[VT,ET], 
-        matches: List[MatchCopyType[VT]]
+        g: BaseGraph[VT,ET],
+        matches: List[MatchCopyType[VT, ET]]
         ) -> rules.RewriteOutputType[VT,ET]:
     """Copy arity-1 spider through their neighbor."""
     rem = []
     types = g.types()
-    for v,w,copy_type,a,alpha,neigh in matches:
+    for v,w,copy_type,a,alpha,neigh_edges in matches:
         rem.append(v)
-        if copy_type == VertexType.BOUNDARY: 
+        if copy_type == VertexType.BOUNDARY:
             g.scalar.add_power(1)
             continue # Don't have to do anything more for this case
         rem.append(w)
         if vertex_is_zx(types[w]):
             if a: g.scalar.add_phase(alpha)
-            g.scalar.add_power(-(len(neigh)-1))
+            g.scalar.add_power(-(len(neigh_edges)-1))
         else: #types[w] == H_BOX
             if copy_type == VertexType.Z:
                 g.scalar.add_power(1)
             else:
-                g.scalar.add_power(-(len(neigh)-2))
+                g.scalar.add_power(-(len(neigh_edges)-2))
                 if alpha != 1:
                     g.scalar.add_power(-2)
                     g.scalar.add_node(alpha+1)
-        for n in neigh: 
+        for edge in neigh_edges:
+            st = g.edge_st(edge)
+            n = st[0] if st[1] == w else st[1]
             r = 0.7*g.row(w) + 0.3*g.row(n)
             q = 0.7*g.qubit(w) + 0.3*g.qubit(n)
-            
+
             u = g.add_vertex(copy_type, q, r, a)
-            e = g.edge(n,w)
-            et = g.edge_type(e)
+            et = g.edge_type(edge)
             g.add_edge((n,u), et)
 
     return ({}, rem, [], True)