Databases
StackOverflow2013
Postsdbo
PONullReferenceException on type initializer
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PONullReferenceException on type initializer
    primarykey
    data
    text
    <p>I was playing with F# types and datastructures in the following code (I'm using Monodevelop on a Mac and this only happens in the Interactive):</p> <pre><code>type UnbalancedSet&lt;'a&gt; = | E | T of UnbalancedSet&lt;'a&gt; * 'a * UnbalancedSet&lt;'a&gt; let rec insert x = function | E -&gt; T(E, x, E) | T(a, y, b) as s -&gt; if x &lt; y then T(insert x a, y, b) elif x &gt; y then T(a, y, insert x b) else s </code></pre> <p>It works great with simple types as ints floats and chars but when it comes to strings or tuples it gives the following error:</p> <pre><code>let a = insert (3, 9) E;; System.TypeInitializationException: An exception was thrown by the type initializer for UnbalancedSet`1 ---&gt; System.NullReferenceException: Object reference not set to an instance of an object at FSI_0004+UnbalancedSet`1[System.Tuple`2[System.Int32,System.Int32]]..cctor () [0x00000] in &lt;filename unknown&gt;:0 --- End of inner exception stack trace --- at &lt;StartupCode$FSI_0004&gt;.$FSI_0004.main@ () [0x00000] in &lt;filename unknown&gt;:0 at (wrapper managed-to-native) System.Reflection.MonoMethod:InternalInvoke (System.Reflection.MonoMethod,object,object[],System.Exception&amp;) at System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x00000] in &lt;filename unknown&gt;:0 Stopped due to error </code></pre> <p>I don't understand what's going on. I expected this code to work since the type is comparable. Any clues?</p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. UScurial
    1. UScurial
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. PONullReferenceException on type initializer
      1. USsvick
      1. VTFavorite
    2. VO
      singulars
      1. PONullReferenceException on type initializer
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. PONullReferenceException on type initializer
      1. This table or related slice is empty.
      1. VTUpMod
    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.

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