StackOverflow2013

Note that there are some explanatory texts on larger screens.

plurals

PO
primarykey
Id
3911879
data
AcceptedAnswerId
0
AnswerCount
0
ClosedDate
CommentCount
0
CommunityOwnedDate
CreationDate
2010-10-12T05:20:57.147
FavoriteCount
0
LastActivityDate
2010-10-12T05:20:57.147
LastEditDate
LastEditorUserId
0
OwnerUserId
271324
ParentId
3911103
PostTypeId
2
Score
5
ViewCount
0
LastEditorDisplayName
text
Body
There is not only one possible solution, but I will stay close to your code. Since this is homework, I will not give you a working answer, but I will try to give you some things to think about, and give detailed pointers: Try to understand what your code does and what you really want it to do: <pre><code>(defun remove-all (a l) (cond ((null l) nil) ((eql (car l) a) (delete a (cdr l))) (t (cons (car l) (delete a (cdr l)))))) </code></pre> (Renamed to <code>remove-all</code> because <code>delete</code> is already taken, and re-indented in a sane manner.) For flat lists, the code seems to work; but how about nested lists? Let's look at an easy example: <ol> <li>What will happen if you evaluate <code>(remove-all 1 '((1)))</code>?</li> <li>What do you want to happen for that input?</li> <li>How can you achieve it?</li> </ol> Let's take a look: <ol> <li>What happens: <ul> <li>The list is not <code>null</code>, go on</li> <li>The <code>car</code> is not <code>eq</code> to <code>1</code> go on</li> <li><code>'(1)</code> gets <code>cons</code>ed to <code>(remove-all '())</code>, yielding <code>'((1))</code></li> </ul> So, it failed to recognize that the <code>car</code> is itself a list which should be searched for matching elements. The problem seems to lie between step one and step two.</li> <li>What should be done: <ul> <li>Check, if the <code>car</code> is itself a list</li> <li>If yes, invoke <code>remove-all</code> on it</li> <li>Then, <code>cons</code> the result to the <code>cdr</code>, which also needs to be "cleaned" (Hint: But only if there is something to <code>cons</code>)</li> </ul></li> <li>How exactly? <ul> <li>Add a <code>cond</code> clause which does the things mentioned under 2 -- Left as homework</li> </ul></li> </ol>
Tags
Title
singulars
PostAcceptedAnswerId
1. This table or related slice is empty.
PostParentId
1. POExtracting a list inside a list
 singulars
 PostTypePostTypeId
 PTQuestion
PostTypePostTypeId
1. PTAnswer
UserLastEditorUserId
1. This table or related slice is empty.
UserOwnerUserId
1. USdanlei
plurals
PostLinksPostIdRelatedPostId
1. This table or related slice is empty.
PostLinksRelatedPostIdPostId
1. This table or related slice is empty.
PostsAcceptedAnswerId
1. POExtracting a list inside a list
 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
 VTUpMod
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.