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Why is Scala's immutable Set not covariant in its type?
...ameter of type A due to the contravariance of functions. Set could potentially be contravariant in A, but this too causes issues when you want to do things like this:
def elements: Iterable[A]
In short, the best solution is to keep things invariant, even for the immutable data structure. You'll...
Python argparse: default value or specified value
...
import argparse
parser = argparse.ArgumentParser()
parser.add_argument('--example', nargs='?', const=1, type=int)
args = parser.parse_args()
print(args)
% test.py
Namespace(example=None)
% test.py --example
Namespace(example=1)
% test.py --example 2
Namespace(example=2)
nargs...
How can I call a custom Django manage.py command directly from a test driver?
...ts.
But if you by some reason cannot decouple logic form command you can call it from any code using call_command method like this:
from django.core.management import call_command
call_command('my_command', 'foo', bar='baz')
...
Global access to Rake DSL methods is deprecated
...
You can "delete" Rake 0.9.1 by running the following command:
gem uninstall rake -v=0.9.1
If you have multiple versions of the gem installed, you'll be prompted to pick a version.
After 0.9.1 was cleaned out, I ran
bundle update rake
and was finally able to create my database files. I was ...
What are type lambdas in Scala and what are their benefits?
...ction of Either[A, B]. The monad typeclass looks like this:
trait Monad[M[_]] {
def point[A](a: A): M[A]
def bind[A, B](m: M[A])(f: A => M[B]): M[B]
}
Now, Either is a type constructor of two arguments, but to implement Monad, you need to give it a type constructor of one argument. The sol...
What is the relationship between UIView's setNeedsLayout, layoutIfNeeded and layoutSubviews?
...fNeeded and layoutSubviews methods? And an example implementation where all three would be used. Thanks.
2 Answers
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Forward function declarations in a Bash or a Shell script?
...
This seems somewhat analogous to what if _ _ name _ _ == "_ _ main _ _": main() does in python
– Sergiy Kolodyazhnyy
Feb 13 '16 at 7:13
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Convert JSON style properties names to Java CamelCase names with GSON
...GSON to convert JSON data I get to a Java object. It works pretty well in all my tests.
The problem is that our real objects have some properties named like is_online. GSON only maps them if they are named totally equal, it would be nice to have GSON convert the names to Java camel case isOnline.
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Why do we need message brokers like RabbitMQ over a database like PostgreSQL?
...ustering options are also available.
In regards to AMQP, I would say a really cool feature is the "exchange", and the ability for it to route to other exchanges. This gives you more flexibility and enables you to create a wide array of elaborate routing typologies which can come in very handy when...
Android Studio needs JDK 7 for Android-L mac
...
Setting the directory to:
/Library/Java/JavaVirtualMachines/jdk1.7.0_60.jdk/Contents/Home
in JDK settings solved my issue. I had the same problem getting started up. Hope this helps!
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