SELECT name, caption as title, year, pages FROM books
UNION
SELECT name, title, year, 0 as pages FROM movies
When combining 2 record sets with different columns then emulate the missing ones with default values.
extern int var;
static int var; /* Undefined behaviour */
C11, §6.2.2, 7 says:
If, within a translation unit, the same identifier appears with both
internal and external linkage, the behavior is undefined.
Note that if an prior declaration of an identifier is visible then it'll have the pri...
Use the yum command to manage packages in Enterprise Linux-based operating systems:
yum install php
This installs a minimal install of PHP including some common features. If you need additional modules, you will need to install them separately. Once again, you can use yum to search for these pac...
For efficiency, data.table offers a way of altering a data.frame or list to make a data.table in-place:
# example data.frame
DF = data.frame(x = letters[1:5], y = 1:5, z = (1:5) > 3)
# modification
setDT(DF)
Note that we do not <- assign the result, since the object DF has been modifi...
In general, UWP is used for making a single application that runs on Windows 10 across many different devices. However, it is also possible to make code tailored to specific devices. You can achieve this in several different ways.
Different XAML Layout
If you want to use a specific layout on for a...
Modifiers are a way to indicate how external objects can access an object's data.
Public
Means any object can access this without restriction
Private
Means only the declaring object can access and view this
Protected
Means only the declaring object and any object that inherits from...
sudo apt-add-repository ppa:brightbox/ruby-ng
Hit Enter to confirm
sudo apt-get update
Then you can install your ruby version of choice (the ppa supports ruby2.0 ruby2.1 ruby2.2 ruby2.3 and legacy versions ruby1.8 ruby1.9.1) Don't forget to include the respective -dev package for your version. Ot...
To see all the facts involving the le relation from the prelude:
Coq < Search le.
le_n: forall n : nat, n <= n
le_S: forall n m : nat, n <= m -> n <= S m
...
max_l: forall n m : nat, m <= n -> Nat.max n m = n
max_r: forall n m : nat, n <= m -> Nat.max n m = m
...
...
The dimension attribute on an object specifies that that object is an array. There are, in Fortran 2008, five array natures:1
explicit shape
assumed shape
assumed size
deferred shape
implied shape
Take the three rank-1 arrays2
integer a, b, c
dimension(5) a ! Explicit shape (default ...
java.lang.ref package provides reference-object classes, which support a limited degree of interaction with the garbage collector.
Java has four main different reference types. They are:
Strong Reference
Weak Reference
Soft Reference
Phantom Reference
1. Strong Reference
This is the usual...
Using the document-ready event can have small performance drawbacks, with delayed execution of up to ~300ms. Sometimes the same behavior can be achieved by execution of code just before the closing </body> tag:
<body>
<span id="greeting"></span> world!
<sc...
Visual Studio also features an available Bundler and Minifier Extension that is capable of handling this process for you. The extension allows you to easily select and bundle the files you need without writing a line of code.
Building Your Bundles
After installing the extension, you select all of ...
type
TIntegerList = class(TList<Integer>)
public
function Sum: Integer;
end;
...
function TIntegerList.Sum: Integer;
var
Item: Integer;
begin
Result := 0;
for Item in Self do
Result := Result + Item;
end;
The minification is used to reduce the size of CSS and Javascript files to speed up download times. This process is done by removing all of the unnecessary white-space, comments, and any other non-essential content from the files.
This process is done automatically when using a ScriptBundle or a St...
This is an example of something that would have been straight up impossible with labels. If you execute the same label multiple times at the same time and they rely on variables that are being defined within them, they very likely interfere and cause unexpected behavior.
Here is how to do it with f...
There are two ways to register a background page in the extension manifest.
The scripts property
In the common case, a background page doesn't require any HTML markup. We can register these kinds of background pages using the scripts property.
In this case, a background page will be generated...
Java provides the instanceof operator to test if an object is of a certain type, or a subclass of that type. The program can then choose to cast or not cast that object accordingly.
Object obj = Calendar.getInstance();
long time = 0;
if(obj instanceof Calendar)
{
time = ((Calendar)obj).ge...
Often times you will need to be able to manage your notifications, by being able to keep track of them and cancel them.
Track a notification
You can assign a UUID (universally unique identifier) to a notification, so you can track it:
Swift
let notification = UILocalNotification()
let uuid = NS...
MY_CONSTANT = "Hello, world"
MY_CONSTANT = "Hullo, world"
The above code results in a warning, because you should be using variables if you want to change their values. However it is possible to change one letter at a time in a constant without a warning, like this:
MY_CONST...
The Java language provides three operator for performing bitwise shifting on 32 and 64 bit integer values. These are all binary operators with the first operand being the value to be shifted, and the second operand saying how far to shift.
The << or left shift operator shifts the value g...
