StackOverflow2013

Note that there are some explanatory texts on larger screens.

plurals

PO
primarykey
Id
17197188
data
AcceptedAnswerId
0
AnswerCount
0
ClosedDate
CommentCount
0
CommunityOwnedDate
CreationDate
2013-06-19T17:04:05.100
FavoriteCount
0
LastActivityDate
2013-06-19T17:22:13.583
LastEditDate
2013-06-19T17:22:13.583
LastEditorUserId
1468366
OwnerUserId
1468366
ParentId
17181274
PostTypeId
2
Score
0
ViewCount
0
LastEditorDisplayName
text
Body
Your second edit indicates that the basic intersection routine will operate using some <code>furthest_along</code> code. You could make use of that, in such a way that normal intersection checks operate on a common base class which includes this <code>furthest_along</code> in its interface. You would need special functions only for special cases, for which you want other algorithms. The following example avoids all dynamic casts and performs two virtual method invocations instead (also known as “<a href="http://en.wikipedia.org/wiki/Double_dispatch#Double_dispatch_in_C.2B.2B" rel="nofollow">double dispatch</a>”, which by the way is also available as a <a href="/questions/tagged/double-dispatch" class="post-tag" title="show questions tagged 'double-dispatch'" rel="tag">double-dispatch</a> tag, so adding that to your question might be useful). <pre><code>struct Geometry { virtual ~Geometry() { } virtual Point furthest_along(Vector& v) const = 0; virtual bool intersects(const Geometry& other) const { return other.intersects_impl(*this); } virtual bool intersects_impl(const Geometry& other) const { // default impl // compute intersection using furthest_along } virtual bool intersects_impl(const Circle& other) const { return intersects_impl(static_cast<const Geometry&>(other)); // use default } }; struct Circle : public Geometry { bool intersects(const Geometry& other) const { return other.intersects_impl(*this); // call intersects_impl(const Circle&) } bool intersects_impl(const Circle& other) const { // do circle-circle intersection } Point furthest_along(Vector& v) const { // implement for default intersection } }; struct Rectangle : public Geometry { Point furthest_along(Vector& v) const { // implement for default intersection } }; </code></pre> If you call <code>a.intersects(b)</code>, then the <code>intersects</code> method will be chosen from the virtual function table of <code>a</code>, whereas the <code>intersects_impl</code> method will be chosen from <code>b</code>. If you want to add a special case for the type combination <code>A</code> and <code>B</code>, you'll have to add <ol> <li>a virtual method <code>Geometry::intersects_impl(const A&)</code>, delegating to the default</li> <li>an override method <code>A::intersects</code> delegating to <code>intersects_impl(const A&)</code></li> <li>an override method <code>B::intersects_impl(const A&)</code> with the actual custom code</li> </ol> If you have to add many types with many special case algorithms, this might amount to a fairly high number of modifications in various places. If, however, most shapes that you add will be using the default implementation, then all you have to do is properly implementing <code>furthest_along</code> for each of these. You can of course do more clever things than this. You can create an intermediate class <code>ConvexGeometry</code> which uses the <code>furthest_along</code> approach, and a class <code>NonConvexGeometry</code> which would provide some means for partitioning into convex pieces. You could implement <code>intersects</code> in both of these and make the implementation in <code>Geometry</code> purely abstract (<code>= 0</code>). You could then avoid <code>intersects_impl(const Geometry&)</code> and instead use <code>intersects_impl(const ConvexGeometry&)</code> and <code>intersects_impl(const NonConvexGeometry&)</code> as the default mechanisms, both of which could be <code>= 0</code> in <code>Geometry</code> and implemented appropriately in <code>ConvexGeometry</code> and <code>NonConvexGeometry</code>. But if you understand the idea behind the above code, then adding these extensions should be simple enough. If not, ask.
Tags
Title
singulars
PostAcceptedAnswerId
1. This table or related slice is empty.
PostParentId
1. POvisitor-like pattern for template objects
 singulars
 PostTypePostTypeId
 PTQuestion
PostTypePostTypeId
1. PTAnswer
UserLastEditorUserId
1. USMvG
UserOwnerUserId
1. USMvG
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. 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.