From: Michael Orlitzky <michael@orlitzky.com>
Date: Fri, 23 Jan 2026 16:50:23 +0000 (-0500)
Subject: mjo/clan: complete the migration to three coordinates
X-Git-Url: https://gitweb.michael.orlitzky.com/?a=commitdiff_plain;h=e84ed3f4b22fd09bb24883061775011adefd309c;p=sage.d.git

mjo/clan: complete the migration to three coordinates

Three coordinates are needed to identify a basis element in general:
(i,j) to identify the component, and then "k" for the basis within
the (i,j)th component.

This should allow us to define HnClan, which has 2d off-diagonal
components.
---

diff --git a/mjo/clan/clan_element.py b/mjo/clan/clan_element.py
index 4aba6d1..6383703 100644
--- a/mjo/clan/clan_element.py
+++ b/mjo/clan/clan_element.py
@@ -50,8 +50,12 @@ class NormalDecompositionElement(ClanElement):
     An element of a :class:`NormalDecomposition`.
 
     These may have additional methods that require knowledge of the
-    coordinates in a normal decomposition.
+    coordinates in a normal decomposition. The basis should follow the
+    Ishi convention with the components (i,j) being ordered
+    lexicographically and then within each component the basis
+    elements (i,j,k) ordered arbitrarily.
     """
+
     def tr(self):
         r"""
         The clan trace of this element; the sum of its diagonal
@@ -243,7 +247,7 @@ class NormalDecompositionElement(ClanElement):
             8
 
         """
-        return self.seq(k)[k,k]
+        return self.seq(k)[k,k,1]
 
 
     def chi(self, k):