Tutorial by Examples: d

// The Option type can either contain Some value or None. fn find(value: i32, slice: &[i32]) -> Option<usize> { for (index, &element) in slice.iter().enumerate() { if element == value { // Return a value (wrapped in Some). return Some(index);...

Inject and reduce are different names for the same thing. In other languages these functions are often called folds (like foldl or foldr). These methods are available on every Enumerable object. Inject takes a two argument function and applies that to all of the pairs of elements in the Array. For...

Discriminated unions in F# offer a a way to define types which may hold any number of different data types. Their functionality is similar to C++ unions or VB variants, but with the additional benefit of being type safe. // define a discriminated union that can hold either a float or a string type...

If the variable contains a value of an immutable type (e.g. a string) then it is okay to assign a default value like this class Rectangle(object): def __init__(self, width, height, color='blue'): self.width = width self.height = height self.color = color d...

Whenever you attempt to retrieve a certain field from a class like so: $animal = new Animal(); $height = $animal->height; PHP invokes the magic method __get($name), with $name equal to "height" in this case. Writing to a class field like so: $animal->height = 10; Will invoke...

A binary is a sequence of unsigned 8-bit bytes. 1> <<1,2,3,255>>. <<1,2,3,255>> 2> <<256,257,258>>. <<0,1,2>> 3> <<"hello","world">>. <<"helloworld">> A bitstring is a generalized ...

Each migration should have an up() method and a down() method. The purpose of the up() method is to perform the required operations to put the database schema in its new state, and the purpose of the down() method is to reverse any operations performed by the up() method. Ensuring that the down() me...

The following code creates a simple user interface containing a single Button that prints a String to the console on click. import javafx.application.Application; import javafx.scene.Scene; import javafx.scene.control.Alert; import javafx.scene.control.Alert.AlertType; import javafx.scene.contr...

.rds and .Rdata (also known as .rda) files can be used to store R objects in a format native to R. There are multiple advantages of saving this way when contrasted with non-native storage approaches, e.g. write.table: It is faster to restore the data to R It keeps R specific information encoded ...

Run-length encoding captures the lengths of runs of consecutive elements in a vector. Consider an example vector: dat <- c(1, 2, 2, 2, 3, 1, 4, 4, 1, 1) The rle function extracts each run and its length: r <- rle(dat) r # Run Length Encoding # lengths: int [1:6] 1 3 1 1 2 2 # valu...

One of the first questions people have when they begin to use PowerShell for scripting is how to manipulate the output from a cmdlet to perform another action. The pipeline symbol | is used at the end of a cmdlet to take the data it exports and feed it to the next cmdlet. A simple example is using...

CSS div { height: 100px; width: 100px; border: 1px solid; transition-property: height, width; transition-duration: 1s, 500ms; transition-timing-function: linear; transition-delay: 0s, 1s; } div:hover { height: 200px; width: 200px; } HTML <div></div> ...

type person = {Name: string; Age: int} with // Defines person record member this.print() = printfn "%s, %i" this.Name this.Age let user = {Name = "John Doe"; Age = 27} // creates a new person user.print() // John Doe, 27

The filter or map functions should often be replaced by list comprehensions. Guido Van Rossum describes this well in an open letter in 2005: filter(P, S) is almost always written clearer as [x for x in S if P(x)], and this has the huge advantage that the most common usages involve predicates tha...

Module is a collection of type declarations, data declarations and procedures. The basic syntax is: module module_name use other_module_being_used ! The use of implicit none here will set it for the scope of the module. ! Therefore, it is not required (although considered good practice...

You may wish to use Model Factories within your seeds. This will create 3 new users. use App\Models\User; class UserTableSeeder extends Illuminate\Database\Seeder{ public function run(){ factory(User::class)->times(3)->create(); } } You may also want to define ...

Artisan is a utility that can help you do specific repetitive tasks with bash commands. It covers many tasks, including: working with database migrations and seeding, clearing cache, creating necessary files for Authentication setup, making new controllers, models, event classes, and a lot more. ...

The following is the original "Hello, World!" program from the book The C Programming Language by Brian Kernighan and Dennis Ritchie (Ritchie was the original developer of the C programming language at Bell Labs), referred to as "K&R": K&R #include <stdio.h> ma...

The MATLAB Profiler is a tool for software profiling of MATLAB code. Using the Profiler, it is possible to obtain a visual representation of both execution time and memory consumption. Running the Profiler can be done in two ways: Clicking the "Run and Time" button in the MATLAB GUI...

Python 3.x3.3 Use yield from if you want to yield all values from another iterable: def foob(x): yield from range(x * 2) yield from range(2) list(foob(5)) # [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1] This works with generators as well. def fibto(n): a, b = 1, 1 while True: ...