Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>This was a conscious design decision to make Set.contains/apply typesafe. You should not be able to have a s:Set[Int] and accidentally do something like s.contains("x") which would always be false so probably not what you intended. Also, Set[T] implements Function[T,Boolean], which is only possible if the apply method does not take an Any.</p> <p>There were endless discussions about this topic on the scala-user mailing list. See for example <a href="https://groups.google.com/forum/#!topic/scala-user/hbxt2TnRii0" rel="nofollow">this</a> or <a href="http://grokbase.com/t/gg/scala-language/1286jy8xce/collections-annoyances-missed-opportunities-for-structural-sharing" rel="nofollow">this</a>.</p> <p>Here is a quote from Paul Phillips from the second discussion that summarizes the rationale very well:</p> <p>"Yes, apply (aliased to contains) is the central operation of Set, whereas contains is indeed "just some method" on Seq.</p> <p>Nobody's saying you don't sometimes want a covariant Set, but on balance, it is more useful invariant."</p> <p>Note that you can always add covariance to sets with an implicit conversion. This means that if you have e.g. a Set[Int] and a method that takes a Set[Any], it will work. But it also means that you can now accidentally call Set[Int].contains("x"), and the compiler will not catch the error (you will always get false).</p> <pre><code>scala&gt; implicit def setIsCovariant[T,U &lt;: T](s:Set[U]):Set[T] = s.asInstanceOf[Set[T]] setIsCovariant: [T, U &lt;: T](s: Set[U])Set[T] scala&gt; val s : Set[Int] = Set(1,2,3,4) s: Set[Int] = Set(1, 2, 3, 4) scala&gt; s.contains("x") res0: Boolean = false scala&gt; val a: Set[Any] = s a: Set[Any] = Set(1, 2, 3, 4) </code></pre>
    singulars
    1. This table or related slice is empty.
    1. POWhy is GenSet declared to have invariant type parameter?
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USRüdiger Klaehn
    1. USRüdiger Klaehn
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. POWhy is GenSet declared to have invariant type parameter?
      singulars
      1. PTQuestion
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTAcceptedByOriginator
    1. COOk - can you or someone please give me some examples of doing what I need to do above? Will it take building new collections? (I don't think casting can do the trick even if I wanted to resort to that.) Thanks!
      singulars
      1. PO
      1. USScala Newb
    2. COWell, I just made the code work with collections of [Foo] instead of [- <: Foo]. That seemed best.
      singulars
      1. PO
      1. USScala Newb
 

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.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload