Changes between Version 1 and Version 2 of SandBox

Timestamp:

09/06/11 01:43:40 (13 years ago)

Author:

todd.a

Comment:

--

SandBox

@@ -4 +4 @@
 
 Go ahead, edit it freely.
+
+{{{
+#!cobra
+
+class MruList<of T> implements ICollection<of T>
+    """
+    Store a "most recently used" list of items.
+    Calling .add puts the item at the front of the list.
+    Also, .add will not grow the list when it already contains a given item.
+    An MruList is enumerable, so you can use for loops on it, .toList, .numbered, .reversed, etc.
+
+    Because an MruList uses a dictionary internally for some caching, the item T should implement
+    both .equals and .getHashCode.
+    
+    to-do: support a max capacity
+    """
+
+    var _list = LinkedList<of T>()
+    var _dict = Dictionary<of T, LinkedListNode<of T>>()
+
+    def add(item as T)
+        if _list.count <= 4  # to-do: test what the real switchover should be
+            _list.remove(item)
+        else
+            lln as LinkedListNode<of T>?
+            if _dict.tryGetValue(item, out lln), _list.remove(lln)
+        _dict[item] = _list.addFirst(item) to !
+        assert _list.count == _dict.count
+
+    def clear
+        _list.clear
+        _dict.clear
+        assert _list.count == _dict.count
+
+    def contains(item as T) as bool
+        return _list.contains(item)
+
+    def copyTo(array as T[], arrayIndex as int)
+        _list.copyTo(array, arrayIndex)
+
+    get count as int
+        return _list.count
+
+    def getEnumerator as IEnumerator<of T>
+        return _list.getEnumerator
+
+    def getEnumerator as System.Collections.IEnumerator
+        implements System.Collections.IEnumerable
+        return .getEnumerator
+
+    get isReadOnly as bool
+        return false
+
+    def remove(item as T) as bool
+        _dict.remove(item)
+        r = _list.remove(item)
+        assert _list.count == _dict.count
+        return r
+
+    def set(items as IList<of T>)
+        """
+        Set all the items in the MRU list.
+        There is no reversal of the items like if you called .add for each item.
+        Repeated items are forbidden and will cause an exception.
+        """
+        .clear
+        for item in items, _dict[item] = _list.addLast(item) to !
+        trace _dict.count, _list.count
+        if _dict.count <> _list.count, throw InvalidOperationException('repeated items in set list')
+
+
+class TestMruList
+
+    test
+        ml = MruList<of String>()
+        assert ml.count == 0
+        ml.add('foo')
+        assert ml.count == 1
+        assert ml.contains('foo')
+        assert not ml.contains('bar')
+        assert ml.toList == ['foo']
+        ml.clear
+        assert ml.count == 0
+        
+        ml = MruList<of String>()
+        ml.add('foo')
+        ml.add('bar')
+        assert ml.contains('foo')
+        assert ml.contains('bar')
+        assert ml.toList == ['bar', 'foo']  # note the mru order
+        ml.add('bar')
+        assert ml.toList == ['bar', 'foo']
+        ml.add('bar')
+        assert ml.toList == ['bar', 'foo']
+        ml.add('foo')
+        assert ml.toList == ['foo', 'bar']
+        ml.add('baz')
+        assert ml.toList == ['baz', 'foo', 'bar']
+
+        ml = MruList<of String>()
+        ml.set(['foo', 'bar', 'baz'])
+        assert ml.toList == ['foo', 'bar', 'baz']
+        ml.add('buzz')
+        assert ml.toList == ['buzz', 'foo', 'bar', 'baz']
+        ml.set(['foo', 'bar', 'baz'])
+        assert ml.toList == ['foo', 'bar', 'baz']
+
+}}}