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Site does not exist error for a2ensite
...
You probably updated your Ubuntu installation and one of the updates included the upgrade of Apache to version 2.4.x
In Apache 2.4.x the vhost configuration files, located in the /etc/apache2/sites-available directory, must have the .conf extension.
Using term...
How to format a number as percentage in R?
...s pointed out by @DzimitryM, percent() has been "retired" in favor of label_percent(), which is a synonym for the old percent_format() function.
label_percent() returns a function, so to use it, you need an extra pair of parentheses.
library(scales)
x <- c(-1, 0, 0.1, 0.555555, 1, 100)
label_pe...
How to find a Java Memory Leak
... supposed to be able to find the root reference ( ref ) or whatever it is called. Basically, I can tell that there are several hundred megabytes of hash table entries ([java.util.HashMap$Entry or something like that), but maps are used all over the place... Is there some way to search for large maps...
Proper use cases for Android UserManager.isUserAGoat()?
...changed in API 21.
/**
* Used to determine whether the user making this call is subject to
* teleportations.
* @return whether the user making this call is a goat
*/
public boolean isUserAGoat() {
return false;
}
It looks like the method has no real use for us as developers. Someone has ...
How can I use a search engine to search for special characters? [closed]
...ace before it, in which case it is a negative sign.)
The underscore symbol _ is not ignored when it connects two words, e.g. [ quick_sort ].
As such, it is not well suited for these types of searchs. Google Code however does have syntax for searching through their code projects, that includes a ro...
How can I convert string date to NSDate?
... */
let date = dateFormatter.dateFromString(/* your_date_string */)
For further query, check NSDateFormatter and DateFormatter classes of Foundation framework for Objective-C and Swift, respectively.
Swift 3 and later (Swift 4 included)
let dateFormatter = DateFormatter()...
What are the differences between struct and class in C++?
...
That's not really a second difference, it's just that the question stated the difference incompletely. All subobjects are private by default when using the class, public by default with struct, and both define a class type.
...
What are the advantages of using a schema-free database like MongoDB compared to a relational databa
...ire several tables to properly represent in a relational db. This is especially useful if your data is immutable.
Deep query-ability. MongoDB supports dynamic queries on documents using a document-based query language that's nearly as powerful as SQL.
No schema migrations. Since MongoDB is schema-...
Check if a class is derived from a generic class
...s GenericClassBase, you could ask the same question without any trouble at all like this:
typeof(Test).IsSubclassOf(typeof(GenericClassBase))
IsSubclassOf()
My testing indicates that IsSubclassOf() does not work on parameterless generic types such as
typeof(GenericClass<>)
whereas it...
Setting Authorization Header of HttpClient
...ent = new HttpClient())
{
client.DefaultRequestHeaders.Authorization = _username.ToAuthHeaderValue(_password);
}
Again I think 2 above options make the client using statement a bit less repetitive. Keep in mind that it's best practice to reuse the HttpClient if you are making multiple http ca...