add

sugar/lib/crdt.dart

@@ -1,2 +1,2 @@
 export 'src/crdt/string_index.dart';
-export 'src/crdt/string_index_set.dart';
+export 'src/crdt/string_indexed_list.dart';

sugar/lib/src/crdt/string_indexed_list.dart

@@ -0,0 +1,78 @@
+import 'dart:collection';
+
+import 'package:sugar/sugar.dart';
+
+class Sil<E> extends Iterable<E> {
+
+  /// Whether to strictly validate a string index's format. True by default.
+  final bool strict;
+
+  final SplayTreeMap<String, E> _map;
+  final HashMap<E, String> _inverse;
+  final List<E> _list;
+  final bool Function(E, E) _equals;
+  final int Function(E) _hash;
+
+  Sil._(
+    this._map,
+    this._inverse,
+    this._list,
+    this._equals,
+    this._hash, {
+    required this.strict,
+  });
+
+
+  bool put(String index, E element) {
+    if (_inverse.containsKey(element)) {
+      return false;
+    }
+
+    final old = _map[index];
+    if (old == null) {
+      if (_map.firstValueAfter(index) case final after?) {
+        _list.insert(_list.indexWhere((e) => _equals(e, after)), element);
+
+      } else {
+        _list.add(element);
+      }
+
+      _map[index] = element;
+      _inverse[element] = index;
+
+    } else {
+      _map[index] = element;
+      _inverse.remove(old);
+      _inverse[element] = index;
+      _list[_list.indexWhere((e) => _equals(e, old))] = element;
+    }
+
+    return true;
+  }
+
+
+  int indexOf(E element) => _list.indexOf(element);
+
+  String? stringIndexOf(E element) => _inverse[element];
+
+
+  void operator []= (int index, E element) {
+    if (_inverse.containsKey(element)) {
+      return;
+    }
+
+    final old = _list[index];
+    final string = _inverse.remove(old)!;
+
+    _map[string] = element;
+    _inverse[element] = string;
+    _list[index] = element;
+  }
+
+  E operator [] (int index) => _list[index];
+
+
+  @override
+  Iterator<E> get iterator => _list.iterator;
+
+}

sugar/test/src/crdt/string_index_test.dart

@@ -1,6 +1,5 @@
 import 'dart:math';
 
-import 'package:sugar/src/crdt/string_index.dart';
 import 'package:sugar/sugar.dart';
 import 'package:test/test.dart';