The Sandbox

This is just a page to practice and learn WikiFormatting.

Go ahead, edit it freely.

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
            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
        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
        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.
        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

        ml = MruList<of String>()
        assert ml.count == 0
        assert ml.count == 1
        assert ml.contains('foo')
        assert not ml.contains('bar')
        assert ml.toList == ['foo']
        assert ml.count == 0
        ml = MruList<of String>()
        assert ml.contains('foo')
        assert ml.contains('bar')
        assert ml.toList == ['bar', 'foo']  # note the mru order
        assert ml.toList == ['bar', 'foo']
        assert ml.toList == ['bar', 'foo']
        assert ml.toList == ['foo', 'bar']
        assert ml.toList == ['baz', 'foo', 'bar']

        ml = MruList<of String>()
        ml.set(['foo', 'bar', 'baz'])
        assert ml.toList == ['foo', 'bar', 'baz']
        assert ml.toList == ['buzz', 'foo', 'bar', 'baz']
        ml.set(['foo', 'bar', 'baz'])
        assert ml.toList == ['foo', 'bar', 'baz']

Try lists:

  1. one
  2. two
  • point 1
  • point 2
  1. alpha
  2. beta

Try some code:

@args 2.0gtk-sharp-2.0

use Gtk

class MyWindow inherits Window

    def onDeleteEvent(obj, args as DeleteEventArgs)

and an image: