There is also a way to have a single method accept a covariant argument, instead of having the whole trait covariant. This may be necessary because you would like to use T in a contravariant position, but still have it covariant.
trait LocalVariance[T]{
/// ??? throws a NotImplementedError
de...
int *ptr = nullptr;
*ptr = 1; // Undefined behavior
This is undefined behavior, because a null pointer does not point to any valid object, so there is no object at *ptr to write to.
Although this most often causes a segmentation fault, it is undefined and anything can happen.
Omitting the return statement in a function which is has a return type that is not void is undefined behavior.
int function() {
// Missing return statement
}
int main() {
function(); //Undefined Behavior
}
Most modern day compilers emit a warning at compile time for this kind o...
Events that work with most form elements (e.g., change, keydown, keyup, keypress) do not work with contenteditable.
Instead, you can listen to changes of contenteditable contents with the input event. Assuming contenteditableHtmlElement is a JS DOM object that is contenteditable:
contenteditableH...
To add a new unique column email to users, run the following command:
rails generate migration AddEmailToUsers email:string:uniq
This will create the following migration:
class AddEmailToUsers < ActiveRecord::Migration[5.0]
def change
add_column :users, :email, :string
add_index...
It is undefined behavior to access an index that is out of bounds for an array (or standard library container for that matter, as they are all implemented using a raw array):
int array[] = {1, 2, 3, 4, 5};
array[5] = 0; // Undefined behavior
It is allowed to have a pointer pointing to the en...
The default property getters and setters can be overridden:
@interface TestClass
@property NSString *someString;
@end
@implementation TestClass
// override the setter to print a message
- (void)setSomeString:(NSString *)newString {
NSLog(@"Setting someString to %@", newS...
Assuming a source file of hello_world.v and a top level module of hello_world. The code can be run using various simulators. Most simulators are compiled simulators. They require multiple steps to compile and execute.
Generally the
First step is to compile the Verilog design.
Second step is to ...
The syntax for Java generics bounded wildcards, representing the unknown type by ? is:
? extends T represents an upper bounded wildcard. The unknown type represents a type that must be a subtype of T, or type T itself.
? super T represents a lower bounded wildcard. The unknown type repres...
A has_many association indicates a one-to-many connection with another model. This association generally is located on the other side of a belongs_to association.
This association indicates that each instance of the model has zero or more instances of another model.
For example, in an application ...
For programmers coming from GCC or Clang to Visual Studio, or programmers more comfortable with the command line in general, you can use the Visual C++ compiler from the command line as well as the IDE.
If you desire to compile your code from the command line in Visual Studio, you first need to set...
DataFrame:
import pandas as pd
import numpy as np
np.random.seed(5)
df = pd.DataFrame(np.random.randint(100, size=(5, 5)), columns = list("ABCDE"),
index = ["R" + str(i) for i in range(5)])
df
Out[12]:
A B C D E
R0 99 78 61 16 73...
You can also receive regular updates of the user's location; for example, as they move around while using a mobile device. Location tracking over time can be very sensitive, so be sure to explain to the user ahead of time why you're requesting this permission and how you'll use the data.
if (naviga...
Under res folder, create a new folder called "anim" to store your animation resources and put this on that folder.
shakeanimation.xml
<?xml version="1.0" encoding="utf-8"?>
<rotate xmlns:android="http://schemas.android.com/apk/res/android"
and...
