From 771d989670805593049d7c566ca8b3353b262d4c Mon Sep 17 00:00:00 2001
From: Jerome Kelleher <jk@well.ox.ac.uk>
Date: Thu, 25 Jul 2024 14:36:17 +0100
Subject: [PATCH] Update the class definitions

---
 algorithms.py | 26 ++++++++++++++------------
 1 file changed, 14 insertions(+), 12 deletions(-)

diff --git a/algorithms.py b/algorithms.py
index d83faf5b1..d5fcbb478 100644
--- a/algorithms.py
+++ b/algorithms.py
@@ -1,6 +1,8 @@
 """
 Python version of the simulation algorithm.
 """
+from __future__ import annotations
+
 import argparse
 import dataclasses
 import heapq
@@ -111,6 +113,9 @@ def find(self, v):
         return j + 1
 
 
+# Once we drop support for 3.9 we can use slots=True to prevent
+# writing extra attrs.
+@dataclasses.dataclass  # (slots=True)
 class Segment:
     """
     A class representing a single segment. Each segment has a left
@@ -118,16 +123,15 @@ class Segment:
     next, giving the next in the chain.
     """
 
-    def __init__(self, index):
-        self.left = None
-        self.right = None
-        self.node = None
-        self.prev = None
-        self.next = None
-        self.index = index
-        self.population = None
-        self.label = 0
-        self.lineage = None
+    index: int
+    left: float = 0
+    right: float = 0
+    node: int = -1
+    prev: Segment = None
+    next: Segment = None  # noqa: A003
+    lineage: Lineage = None
+    population: int = -1
+    label: int = 0
 
     def __repr__(self):
         return repr((self.left, self.right, self.node))
@@ -1070,7 +1074,6 @@ def alloc_segment(
         prev=None,
         next=None,  # noqa: A002
         label=0,
-        hull=None,
     ):
         """
         Pops a new segment off the stack and sets its properties.
@@ -1083,7 +1086,6 @@ def alloc_segment(
         s.next = next
         s.prev = prev
         s.label = label
-        s.hull = hull
         return s
 
     def alloc_lineage(self, head):