Tutorial by Examples: var

Variadic Arguments

There are two parts of a class: the interface and the implementation. The interface is the exposed functionality of the class. Its public methods and variables are part of the interface. The implementation is the internal workings of a class. Other classes shouldn't need to know about the implemen...

$ docker run -e "ENV_VAR=foo" ubuntu /bin/bash Both -e and --env can be used to define environment variables inside of a container. It is possible to supply many environment variables using a text file: $ docker run --env-file ./env.list ubuntu /bin/bash Example environment variable...

You can make an UILabel with a dynamic height using auto layout. You need to set the numberOfLines to zero (0), and add a minimal height by setting up a constraints with a relation of type .GreaterThanOrEqual on the .Height attribute iOS 6 Swift label.numberOfLines = 0 let heightConstraint = ...

package main import ( "log" "text/template" "os" ) type Person struct{ MyName string MyAge int } var myTempContents string= ` This person's name is : {{.MyName}} And he is {{.MyAge}} years old. ` func main() { t,err := temp...

To assign variables from the command-line, -v can be used: $ awk -v myvar="hello" 'BEGIN {print myvar}' hello Note that there are no spaces around the equal sign. This allows to use shell variables: $ shell_var="hello" $ awk -v myvar="$shell_var" 'BEGIN {print m...

Destructuring allows us to refer to one key in an object, but declare it as a variable with a different name. The syntax looks like the key-value syntax for a normal JavaScript object. let user = { name: 'John Smith', id: 10, email: '[email protected]', }; let {user: userName, id: us...

[a-b] where a and b are digits in the range 0 to 9 [3-7] will match a single digit in the range 3 to 7. Matching multiple digits \d\d will match 2 consecutive digits \d+ will match 1 or more consecutive digits \d* will match 0 or more consecutive digits \d{3} will ma...

DATA begda TYPE sy-datum.

DATA: begda TYPE sy-datum, endda TYPE sy-datum.

The + symbol marks a type parameter as covariant - here we say that "Producer is covariant on A": trait Producer[+A] { def produce: A } A covariant type parameter can be thought of as an "output" type. Marking A as covariant asserts that Producer[X] <: Producer[Y] prov...

By default all type parameters are invariant - given trait A[B], we say that "A is invariant on B". This means that given two parametrizations A[Cat] and A[Animal], we assert no sub/superclass relationship between these two types - it does not hold that A[Cat] <: A[Animal] nor that A[Ca...

The - symbol marks a type parameter as contravariant - here we say that "Handler is contravariant on A": trait Handler[-A] { def handle(a: A): Unit } A contravariant type parameter can be thought of as an "input" type. Marking A as contravariant asserts that Handler[X] &l...

Because collections are typically covariant in their element type*, a collection of a subtype may be passed where a super type is expected: trait Animal { def name: String } case class Dog(name: String) extends Animal object Animal { def printAnimalNames(animals: Seq[Animal]) = { anima...

Descriptive names and structure in your code help make comments unnecessary Dim ductWidth As Double Dim ductHeight As Double Dim ductArea As Double ductArea = ductWidth * ductHeight is better than Dim a, w, h a = w * h This is especially helpful when you are copying data from one ...

Object arrays are covariant, which means that just as Integer is a subclass of Number, Integer[] is a subclass of Number[]. This may seem intuitive, but can result in surprising behavior: Integer[] integerArray = {1, 2, 3}; Number[] numberArray = integerArray; // valid Number firstElement = numb...

Broadcast variables are read only shared objects which can be created with SparkContext.broadcast method: val broadcastVariable = sc.broadcast(Array(1, 2, 3)) and read using value method: val someRDD = sc.parallelize(Array(1, 2, 3, 4)) someRDD.map( i => broadcastVariable.value.apply(...

:root { --red: #b00; --blue: #4679bd; --grey: #ddd; } .Bx1 { color: var(--red); background: var(--grey); border: 1px solid var(--red); }

:root { --W200: 200px; --W10: 10px; } .Bx2 { width: var(--W200); height: var(--W200); margin: var(--W10); }

Python 3.x3.0 Python 3 added a new keyword called nonlocal. The nonlocal keyword adds a scope override to the inner scope. You can read all about it in PEP 3104. This is best illustrated with a couple of code examples. One of the most common examples is to create function that can increment: def c...