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// Copyright (c) 2024, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
/// Extension type that uses a list as a stack.
extension type LocalStack<T>(List<T> _list) {
/// Return `true` if the stack is not empty.
///
/// ```
/// DartDocTest(LocalStack<int>([]).hasCurrent, false)
/// DartDocTest(LocalStack<int>([0]).hasCurrent, true)
/// DartDocTest(LocalStack<int>([0, 1]).hasCurrent, true)
/// ```
bool get hasCurrent => _list.isNotEmpty;
/// Return the current top of the stack.
///
/// ```
/// DartDocTest(LocalStack<int>([0]).current, 0)
/// DartDocTest(LocalStack<int>([0, 1]).current, 1)
/// ```
T get current => _list.last;
/// Return `true` if the stack has more than one element.
///
/// ```
/// DartDocTest(LocalStack<int>([]).hasPrevious, false)
/// DartDocTest(LocalStack<int>([0]).hasPrevious, false)
/// DartDocTest(LocalStack<int>([0, 1]).hasPrevious, true)
/// ```
bool get hasPrevious => _list.length > 1;
/// Returns the second-most element on the stack.
///
/// ```
/// DartDocTest(LocalStack<int>([0, 1]).previous, 0)
/// DartDocTest(LocalStack<int>([0, 1, 2]).previous, 1)
/// ```
T get previous => _list[_list.length - 2];
/// Puts [element] on the top of the stack.
///
/// ```
/// DartDocTest((LocalStack<int>([])..push(0)).current, 0)
/// DartDocTest((LocalStack<int>([])..push(0)..push(1)).current, 1)
/// DartDocTest(
/// (LocalStack<int>([])..push(0)..pop()..push(1)).hasPrevious,
/// false
/// )
/// ```
void push(T element) {
_list.add(element);
}
/// Pops the top of the stack.
///
/// ```
/// DartDocTest(LocalStack<int>([0]).pop(), 0)
/// DartDocTest((LocalStack<int>([0, 1, 2])..pop()).pop(), 1)
/// ```
T pop() {
return _list.removeLast();
}
}