From aaf0925712c1d0ca57b8e2bb52103824b911bbf3 Mon Sep 17 00:00:00 2001
From: Nao Pross <np@0hm.ch>
Date: Wed, 6 Mar 2024 12:08:23 +0100
Subject: Move algebra into abc.Expr

since shape is already there, might as well simplify
---
 mdpoly/abc.py | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/mdpoly/abc.py b/mdpoly/abc.py
index 0a2e783..6637db5 100644
--- a/mdpoly/abc.py
+++ b/mdpoly/abc.py
@@ -4,10 +4,17 @@ from .index import Number, Shape, MatrixIndex, PolyIndex
 from .constants import NUMERICS_EPS
 from .util import iszero
 
-from typing import Self, Iterable, Sequence, Protocol 
+from typing import Self, Iterable, Sequence
+from enum import Enum, auto
 from abc import ABC, abstractmethod
 
 
+class Algebra(Enum):
+    """ Types of algebras. """
+    poly_ring = auto()
+    matrix_ring = auto()
+
+
 class Leaf(ABC):
     """ Leaf of the binary tree. """
     name: str
@@ -25,6 +32,10 @@ class Expr(ABC):
     @abstractmethod
     def right(self) -> Self | Leaf: ...
 
+    @property
+    @abstractmethod
+    def algebra(self) -> Algebra: ...
+
     @property
     @abstractmethod
     def shape(self) -> Shape:
-- 
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