From d1e0154c0c2cc6f929e25f576332adafe4c19994 Mon Sep 17 00:00:00 2001
From: Johnnie Gray <johnniemcgray@gmail.com>
Date: Thu, 30 Nov 2023 14:05:03 -0800
Subject: [PATCH] TN.draw: show 'hyper outer' indices dangling

---
 quimb/tensor/drawing.py | 38 +++++++++++++++++++++++---------------
 1 file changed, 23 insertions(+), 15 deletions(-)

diff --git a/quimb/tensor/drawing.py b/quimb/tensor/drawing.py
index 4136655d..c1f5b2ba 100644
--- a/quimb/tensor/drawing.py
+++ b/quimb/tensor/drawing.py
@@ -309,7 +309,10 @@ def draw_tn(
         # compute a label for this index
         if ishyper:
             # each tensor connects to the dummy node represeting the hyper edge
-            pairs = ((tid, ix) for tid in tids)
+            pairs = [(tid, ix) for tid in tids]
+            if isouter and len(tids) > 1:
+                # 'hyper outer' index
+                pairs.append((("outer", ix), ix))
             # hyper labels get put on dummy node
             label = ""
 
@@ -364,24 +367,29 @@ def draw_tn(
             edges[pair]["label_color"] = label_color
             edges[pair]["label_fontfamily"] = font_family
 
-            # tensor side can always have an incoming arrow
-            tl_left_inds = tn.tensor_map[pair[0]].left_inds
-            edges[pair]["arrow_left"].append(
-                show_left_inds
-                and (tl_left_inds is not None)
-                and (ix in tl_left_inds)
-            )
-            if ishyper:
-                # hyper edge can't have an incoming arrow
+            if isinstance(pair[0], tuple):
+                # dummy hyper outer edge - no arrows
+                edges[pair]["arrow_left"].append(False)
                 edges[pair]["arrow_right"].append(False)
             else:
-                # standard edge can
-                tr_left_inds = tn.tensor_map[pair[1]].left_inds
-                edges[pair]["arrow_right"].append(
+                # tensor side can always have an incoming arrow
+                tl_left_inds = tn.tensor_map[pair[0]].left_inds
+                edges[pair]["arrow_left"].append(
                     show_left_inds
-                    and (tr_left_inds is not None)
-                    and (ix in tr_left_inds)
+                    and (tl_left_inds is not None)
+                    and (ix in tl_left_inds)
                 )
+                if ishyper:
+                    # hyper edge can't have an incoming arrow
+                    edges[pair]["arrow_right"].append(False)
+                else:
+                    # standard edge can
+                    tr_left_inds = tn.tensor_map[pair[1]].left_inds
+                    edges[pair]["arrow_right"].append(
+                        show_left_inds
+                        and (tr_left_inds is not None)
+                        and (ix in tr_left_inds)
+                    )
 
     # parse all tensors / nodes
     for tid, t in tn.tensor_map.items():