StackOverflow2013

Note that there are some explanatory texts on larger screens.

plurals

PORefer generic without type parameter in Scala
primarykey
Id
18602656
data
AcceptedAnswerId
18604396
AnswerCount
1
ClosedDate
CommentCount
0
CommunityOwnedDate
CreationDate
2013-09-03T22:43:12.393
FavoriteCount
0
LastActivityDate
2013-09-11T18:31:45.093
LastEditDate
2013-09-11T18:31:45.093
LastEditorUserId
1037788
OwnerUserId
1037788
ParentId
0
PostTypeId
1
Score
0
ViewCount
437
LastEditorDisplayName
text
Body
I am creating a tree structure in Scala, trying to implement the following type restrictions: <ol> <li>Non-root nodes are one of three types - Time Node, Start Node or End Node</li> <li>Root node only has children of type Time Node</li> <li>Time Nodes only have children of type Start Node</li> <li>Start Nodes only have children of type End Node</li> <li>End nodes may have children of type Start Node or Time Node</li> </ol> These are my type definitions: <pre><code>trait TreeNode[U] { val children:HashSet[NonRootNode[U]] def addChild(c:NonRootNode[U]) } class NonRootNode[T <: TreeNode[T]] extends TreeNode[T] { var passengers:Set[Passenger] = Set() val children:HashSet[T] = new HashSet[T] def addChild(c:T) = { children.add(c) } } case class RootNode extends TreeNode[TimeNode] { val children:HashSet[TimeNode] = new HashSet[TimeNode] def addChild(c:TimeNode) = { children.add(c) } } case class TimeNode(time:Int) extends NonRootNode[StartNode] { } case class StartNode(l:Option[String]) extends NonRootNode[EndNode] { } case class EndNode(l:Option[String]) extends NonRootNode { } </code></pre> First, does this implement requirements 1-4 correctly? Second, is there a way to implement requirement 5 here in the definition? Is there ANY way to implement this requirement, as this would require a heterogeneous set to store children references. EDIT: Types RootNode and EndNode would need a method like the following: <pre><code>trait ParentOfTimeNode extends TreeNode{ //type ChildType = TimeNode def addTimeNodes(startTime:Int, maxTime:Int) = { for(i <- startTime to maxTime) { this.addChild(new TimeNode(i)) } } } </code></pre> Without that line commented, the line that screams is: <pre><code>case class EndNode(l:Option[String]) extends NonRootNode with ParentOfTimeNode{ type ChildType = NonRootNode with IntervalMarker } </code></pre> because of an obvious type match. With the line commented, this.addChild screams since it is bound by ChildType which is undefined.
Tags
<scala><generics>
Title
Refer generic without type parameter in Scala
singulars
PostAcceptedAnswerId
1. PO
 singulars
 PostTypePostTypeId
 PTAnswer
PostParentId
1. This table or related slice is empty.
PostTypePostTypeId
1. PTQuestion
UserLastEditorUserId
1. USnavjotk
UserOwnerUserId
1. USnavjotk
plurals
PostLinksPostIdRelatedPostId
1. This table or related slice is empty.
PostLinksRelatedPostIdPostId
1. This table or related slice is empty.
PostsAcceptedAnswerId
1. This table or related slice is empty.
PostsParentIdCreationDate
1. PO
 singulars
 PostTypePostTypeId
 PTAnswer
VotesPostIdCreationDate
1. This table or related slice is empty.
CommentsPostId
1. This table or related slice is empty.

Querying!

Guidance

A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.