StackOverflow2013

Note that there are some explanatory texts on larger screens.

plurals

PO
primarykey
Id
19871737
data
AcceptedAnswerId
0
AnswerCount
0
ClosedDate
CommentCount
0
CommunityOwnedDate
CreationDate
2013-11-09T02:31:57.877
FavoriteCount
0
LastActivityDate
2013-11-09T02:31:57.877
LastEditDate
LastEditorUserId
0
OwnerUserId
343414
ParentId
19867055
PostTypeId
2
Score
1
ViewCount
0
LastEditorDisplayName
text
Body
I tried to prepare an answer that's suitable for the question. I'm going to assume that all the stuff like <code>up(3)</code> was really supposed to be s-expressions like <code>(up 3)</code>. If not, too bad. You didn't say what the desired output of your example was. I'm going to hope my math is OK and stipulate that it's position (14 -7). The problem seemed to assume that only programs starting with <code>(move (0 0) ...)</code> are legal. I seized that assumption; I ain't letting go. With that prelude, I present my interpretation of the homework exercise: The Horrible Little Love Child of <code>printf</code> and <code>eval</code>. <pre><code>#lang racket ;; the current position and functions to move it (struct pos (x y) #:transparent) (define the-pos (make-parameter (pos 0 0))) (define (dx f n) (match (the-pos) [(pos x y) (the-pos (pos (f x n) y))])) (define (dy f n) (match (the-pos) [(pos x y) (the-pos (pos x (f y n)))])) (define (left n) (dx - n)) (define (right n) (dx + n)) (define (up n) (dy - n)) (define (down n) (dy + n)) ;; namespace for `eval` (define-namespace-anchor a) (define ns (namespace-anchor->namespace a)) ;; start holding your nose (define (run str . args) (define as (for/list ([a args]) (read (open-input-string a)))) (match (read (open-input-string str)) [`(move (0 0) ,xs ...) (for ([x xs]) (define n (match (symbol->string x) [(pregexp "^arg(\\d)$" (list _ n)) (string->number n)] [else (error 'run "bad argN")])) (unless (< -1 n (length as)) (error 'run "bad argN")) (eval (list-ref as n) ns)) (eval '(the-pos) ns)])) ;; a unit test to confirm our true evi^Hal (require rackunit) (the-pos (pos 0 0)) (check-equal? (run "(move (0 0) arg0 arg1 arg2 arg3 arg4 arg5 arg6)" "(up 3)" "(right 5)" "(right 4)" "(down 2)" "(up 6)" "(right 2)" "(right 3)") (pos 14 -7)) ;; and since we went through all the argN nonsense, the reverse: (the-pos (pos 0 0)) (check-equal? (run "(move (0 0) arg6 arg5 arg4 arg3 arg2 arg1 arg0)" "(right 3)" "(right 2)" "(up 6)" "(down 2)" "(right 4)" "(right 5)" "(up 3)") (pos 14 -7)) ;; not that it matters with addition and subtraction...why am I even... </code></pre>
Tags
Title
singulars
PostAcceptedAnswerId
1. This table or related slice is empty.
PostParentId
1. POScheme program parameters
 singulars
 PostTypePostTypeId
 PTQuestion
PostTypePostTypeId
1. PTAnswer
UserLastEditorUserId
1. This table or related slice is empty.
UserOwnerUserId
1. USGreg Hendershott
plurals
PostLinksPostIdRelatedPostId
1. This table or related slice is empty.
PostLinksRelatedPostIdPostId
1. This table or related slice is empty.
PostsAcceptedAnswerId
1. POScheme program parameters
 singulars
 PostTypePostTypeId
 PTQuestion
PostsParentIdCreationDate
1. This table or related slice is empty.
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.