| // Copyright (c) 2016, 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. |
| |
| // @dart = 2.9 |
| |
| /// Dart test verifying that the parser can handle type parameterization of |
| /// method declarations and method invocations. Slightly adjusted version of |
| /// code from DEP #22. |
| |
| library generic_methods_test; |
| |
| import "package:expect/expect.dart"; |
| |
| class BinaryTreeNode<K extends Comparable<K>, V> { |
| final K _key; |
| final V _value; |
| final BinaryTreeNode<K, V> _left; |
| final BinaryTreeNode<K, V> _right; |
| |
| BinaryTreeNode(this._key, this._value, |
| {BinaryTreeNode<K, V> left: null, BinaryTreeNode<K, V> right: null}) |
| : _left = left, |
| _right = right; |
| |
| // Use fresh type variables. |
| static BinaryTreeNode<K2, V2> insertOpt<K2 extends Comparable<K2>, V2>( |
| BinaryTreeNode<K2, V2> t, K2 key, V2 value) { |
| return (t == null) ? new BinaryTreeNode(key, value) : t.insert(key, value); |
| } |
| |
| BinaryTreeNode<K, V> insert(K key, V value) { |
| int c = key.compareTo(_key); |
| if (c == 0) return this; |
| var _insert = (BinaryTreeNode<K, V> node, K key, V value) => |
| insertOpt<K, V>(node, key, value); |
| BinaryTreeNode<K, V> left = _left; |
| BinaryTreeNode<K, V> right = _right; |
| if (c < 0) { |
| left = _insert(_left, key, value); |
| } else { |
| right = _insert(_right, key, value); |
| } |
| return new BinaryTreeNode<K, V>(_key, _value, left: left, right: right); |
| } |
| |
| // Reuse type variables [K], [V] to test shadowing. |
| static BinaryTreeNode<K, U> mapOpt<K extends Comparable<K>, V, U>( |
| BinaryTreeNode<K, V> t, U f(V x)) { |
| return (t == null) ? null : t.map<U>(f); |
| } |
| |
| BinaryTreeNode<K, U> map<U>(U f(V x)) { |
| var _map = (BinaryTreeNode<K, V> t, U f(V x)) => mapOpt<K, V, U>(t, f); |
| return new BinaryTreeNode<K, U>(_key, f(_value), |
| left: _map(_left, f), right: _map(_right, f)); |
| } |
| |
| // Use fresh [K2], shadowing [V]. |
| static S foldPreOpt<K2 extends Comparable<K2>, V, S>( |
| BinaryTreeNode<K2, V> t, S init, S f(V t, S s)) { |
| return (t == null) ? init : t.foldPre<S>(init, f); |
| } |
| |
| S foldPre<S>(S init, S f(V t, S s)) { |
| var _fold = (BinaryTreeNode<K, V> t, S s, S f(V t, S s)) => |
| foldPreOpt<K, V, S>(t, s, f); |
| S s = init; |
| s = f(_value, s); |
| s = _fold(_left, s, f); |
| s = _fold(_right, s, f); |
| return s; |
| } |
| } |
| |
| class BinaryTree<K extends Comparable<K>, V> { |
| final BinaryTreeNode<K, V> _root; |
| |
| BinaryTree._internal(this._root); |
| BinaryTree.empty() : this._internal(null); |
| |
| BinaryTree<K, V> insert(K key, V value) { |
| BinaryTreeNode<K, V> root = |
| BinaryTreeNode.insertOpt<K, V>(_root, key, value); |
| return new BinaryTree<K, V>._internal(root); |
| } |
| |
| BinaryTree<K, U> map<U>(U f(V x)) { |
| BinaryTreeNode<K, U> root = BinaryTreeNode.mapOpt<K, V, U>(_root, f); |
| return new BinaryTree<K, U>._internal(root); |
| } |
| |
| S foldPre<S>(S init, S f(V t, S s)) { |
| return BinaryTreeNode.foldPreOpt<K, V, S>(_root, init, f); |
| } |
| } |
| |
| main() { |
| BinaryTree<num, String> sT = new BinaryTree<num, String>.empty(); |
| |
| sT = sT.insert(0, ""); |
| sT = sT.insert(1, " "); |
| sT = sT.insert(2, " "); |
| sT = sT.insert(3, " "); |
| |
| BinaryTree<num, num> iT = sT.map<num>((String s) => s.length); |
| |
| Expect.equals(iT.foldPre<num>(0, (num i, num s) => i + s), 6); |
| } |