StackOverflow2013

Note that there are some explanatory texts on larger screens.

plurals

PO
primarykey
Id
11852874
data
AcceptedAnswerId
0
AnswerCount
0
ClosedDate
CommentCount
0
CommunityOwnedDate
CreationDate
2012-08-07T19:37:54.400
FavoriteCount
0
LastActivityDate
2012-08-07T19:37:54.400
LastEditDate
LastEditorUserId
0
OwnerUserId
1333025
ParentId
11850821
PostTypeId
2
Score
3
ViewCount
0
LastEditorDisplayName
text
Body
<p>I believe the following example should be close to what you had in mind. First we declare type-level natural numbers. Then we define vectors, which carry their length as a phantom type (see <a href="http://www.haskell.org/pipermail/haskell/2005-May/015815.html" rel="nofollow">Fixed-length vectors in Haskell, Part 1: Using GADTs</a>). And then we define a structure for nested lists of lists of ... which carries the depth as a phantom type. Finally we can define correctly typed <code>rGroupBy</code>.</p> <pre class="lang-hs prettyprint-override"><code>{-# LANGUAGE GADTs #-} {-# LANGUAGE EmptyDataDecls #-} import Data.List (groupBy) data Zero data Succ n data Vec n a where Nil :: Vec Zero a Cons :: a -> Vec n a -> Vec (Succ n) a data LList n a where Singleton :: a -> LList Zero a SuccList :: [LList n a] -> LList (Succ n) a -- Not very efficient, but enough for this example. instance Show a => Show (LList n a) where showsPrec _ (Singleton x) = shows x showsPrec _ (SuccList lls) = shows lls rGroupBy :: Vec n (a -> a -> Bool) -> [a] -> LList (Succ n) a rGroupBy Nil = SuccList . map Singleton rGroupBy (Cons f fs) = SuccList . map (rGroupBy fs) . groupBy f -- TEST ------------------------------------------------------------ main = do let input = ["1.1", "1.2.1", "1.2.2", "2.1", "2.2", "3"] -- don't split anything print $ rGroupBy Nil input -- split on 2 levels print $ rGroupBy (Cons (deweyGroup 1) (Cons (deweyGroup 2) Nil)) input where deweyGroup :: Int -> String -> String -> Bool deweyGroup i a b = a!!idx == b!!idx where idx = 2*(i-1) </code></pre>
Tags
Title
singulars
PostAcceptedAnswerId
1. This table or related slice is empty.
PostParentId
1. POLists of lists of lists
  singulars
  PostTypePostTypeId
  PTQuestion
PostTypePostTypeId
1. PTAnswer
UserLastEditorUserId
1. This table or related slice is empty.
UserOwnerUserId
1. USPetr Pudlák
plurals
PostLinksPostIdRelatedPostId
1. This table or related slice is empty.
PostLinksRelatedPostIdPostId
1. This table or related slice is empty.
PostsAcceptedAnswerId
1. POLists of lists of lists
  singulars
  PostTypePostTypeId
  PTQuestion
PostsParentIdCreationDate
1. This table or related slice is empty.
VotesPostIdCreationDate
1. VO
  singulars
  PostPostId
  PO
  UserUserId
  This table or related slice is empty.
  VoteTypeVoteTypeId
  VTUpMod
2. VO
  singulars
  PostPostId
  PO
  UserUserId
  This table or related slice is empty.
  VoteTypeVoteTypeId
  VTUpMod
3. VO
  singulars
  PostPostId
  PO
  UserUserId
  This table or related slice is empty.
  VoteTypeVoteTypeId
  VTAcceptedByOriginator
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.