To conditionally include a block of code, the preprocessor has several directives (e.g #if, #ifdef, #else, #endif, etc).
/* Defines a conditional `printf` macro, which only prints if `DEBUG`
* has been defined
*/
#ifdef DEBUG
#define DLOG(x) (printf(x))
#else
#define DLOG(x)
#endif
Norm...
Indexes can have several characteristics that can be set either at creation, or by altering existing indexes.
CREATE CLUSTERED INDEX ix_clust_employee_id ON Employees(EmployeeId, Email);
The above SQL statement creates a new clustered index on Employees. Clustered indexes are indexes that dict...
Classes can define properties that instances of the class can use. In this example, Dog has two properties: name and dogYearAge:
class Dog {
var name = ""
var dogYearAge = 0
}
You can access the properties with dot syntax:
let dog = Dog()
print(dog.name)
print(dog.dogYear...
WScript.Echo "Hello world!"
This displays a message on the console if run with cscript.exe (the console host) or in a message box if run with wscript.exe (the GUI host).
If you're using VBScript as the server-side scripting language for a web page (for classic ASP, for example),
Respo...
In MATLAB, the most basic data type is the numeric array. It can be a scalar, a 1-D vector, a 2-D matrix, or an N-D multidimensional array.
% a 1-by-1 scalar value
x = 1;
To create a row vector, enter the elements inside brackets, separated by spaces or commas:
% a 1-by-4 row vector
v = [1, 2...
When working with dictionaries, it's often necessary to access all the keys and values in the dictionary, either in a for loop, a list comprehension, or just as a plain list.
Given a dictionary like:
mydict = {
'a': '1',
'b': '2'
}
You can get a list of keys using the keys() method:
...
Optionals must be unwrapped before they can be used in most expressions. if let is an optional binding, which succeeds if the optional value was not nil:
let num: Int? = 10 // or: let num: Int? = nil
if let unwrappedNum = num {
// num has type Int?; unwrappedNum has type Int
print(&quo...
To allow the use of in for custom classes the class must either provide the magic method __contains__ or, failing that, an __iter__-method.
Suppose you have a class containing a list of lists:
class ListList:
def __init__(self, value):
self.value = value
# Create a set of al...
Import the ElementTree object, open the relevant .xml file and get the root tag:
import xml.etree.ElementTree as ET
tree = ET.parse("yourXMLfile.xml")
root = tree.getroot()
There are a few ways to search through the tree. First is by iteration:
for child in root:
print(child.ta...
(Note: All examples using let are also valid for const)
var is available in all versions of JavaScript, while let and const are part of ECMAScript 6 and only available in some newer browsers.
var is scoped to the containing function or the global space, depending when it is declared:
var x = 4; /...
Final classes
When used in a class declaration, the final modifier prevents other classes from being declared that extend the class. A final class is a "leaf" class in the inheritance class hierarchy.
// This declares a final class
final class MyFinalClass {
/* some code */
}
...
# Set the repository for the scope "myscope"
npm config set @myscope:registry http://registry.corporation.com
# Login at a repository and associate it with the scope "myscope"
npm adduser --registry=http://registry.corporation.com --scope=@myscope
# Install a package &quo...
To create a new branch, while staying on the current branch, use:
git branch <name>
Generally, the branch name must not contain spaces and is subject to other specifications listed here. To switch to an existing branch :
git checkout <name>
To create a new branch and switch to it...
jQuery code is often wrapped in jQuery(function($) { ... }); so that it only runs after the DOM has finished loading.
<script type="text/javascript">
jQuery(function($) {
// this will set the div's text to "Hello".
$("#myDiv").text("Hello"...
These are all equivalent, the code inside the blocks will run when the document is ready:
$(function() {
// code
});
$().ready(function() {
// code
});
$(document).ready(function() {
// code
});
Because these are equivalent the first is the recommended form, the following is a ...
var='0123456789abcdef'
# Define a zero-based offset
$ printf '%s\n' "${var:3}"
3456789abcdef
# Offset and length of substring
$ printf '%s\n' "${var:3:4}"
3456
4.2
# Negative length counts from the end of the string
$ printf '%s\n' "${var:3:-5}"
3456789a...
