Tutorial by Examples: d

Functions are defined with five components: The header, which includes the defn keyword, the name of the function. (defn welcome ....) An optional Docstring that explains and document what the function does. (defn welcome "Return a welcome message to the world" ...) Pa...

Scala can be used as a scripting language. To demonstrate, create HelloWorld.scala with the following content: println("Hello") Execute it with the command-line interpreter (the $ is the command line prompt): $ scala HelloWorld.scala Hello If you omit .scala (such as if you simply...

We can use the :: syntax to dispatch on the type of an argument. describe(n::Integer) = "integer $n" describe(n::AbstractFloat) = "floating point $n" Usage: julia> describe(10) "integer 10" julia> describe(1.0) "floating point 1.0" Unlike m...

In Vue.js, every component instance has its own isolated scope, which means that if a parent component has a child component - the child component has its own isolated scope and the parent component has its own isolated scope. For any medium to large size app, following best practices conventions p...

Sometimes you will have a grid of subplots, and you want to have a single legend that describes all the lines for each of the subplots as in the following image. In order to do this, you will need to create a global legend for the figure instead of creating a legend at the axes level (which wil...

Deferred function calls serve a similar purpose to things like finally blocks in languages like Java: they ensure that some function will be executed when the outer function returns, regardless of if an error occurred or which return statement was hit in cases with multiple returns. This is useful f...

Not always we have liberty to read from or write to a local system path. For example if R code streaming map-reduce must need to read and write to file connection. There can be other scenarios as well where one is going beyond local system and with advent of cloud and big data, this is becoming incr...

std::function can cause significant overhead. Because std::function has [value semantics][1], it must copy or move the given callable into itself. But since it can take callables of an arbitrary type, it will frequently have to allocate memory dynamically to do this. Some function implementations h...

A variable can be downcasted to a subtype using the type cast operators as?, and as!. The as? operator attempts to cast to a subtype. It can fail, therefore it returns an optional. let value: Any = "John" let name = value as? String print(name) // prints Optional("John") ...

Make project (compile modifed and dependent) Windows: Ctrl + F9 OS X / macOS: Cmd + F9 Compile selected file, package or module This is useful to know, as when debugging this shortcut can be used to quickly reload / hotswap classes. Windows: Ctrl + Shift + F9 OS X / macOS: Cmd + Shift + F9 Se...

Basic code completion (the name of any class, method or variable) Windows: Ctrl + Space OS X / macOS: Cmd + Space Smart code completion (filters the list of methods and variables by expected type) Windows: Ctrl + Shift + Space OS X / macOS: Cmd + Shift + Space Overwriting code with a suggestio...

module SomeMixin def foo puts "foo!" end end class Bar include SomeMixin def baz puts "baz!" end end b = Bar.new b.baz # => "baz!" b.foo # => "foo!" # works thanks to the mixin Now Bar is a mix of it...

You can read an a binary file using this piece of code in all recent versions of Java: Java SE 1.4 File file = new File("path_to_the_file"); byte[] data = new byte[(int) file.length()]; DataInputStream stream = new DataInputStream(new FileInputStream(file)); stream.readFully(data); s...

A basic AppComponent that depends on a single AppModule to provide application-wide singleton objects. @Singleton @Component(modules = AppModule.class) public interface AppComponent { void inject(App app); Context provideContext(); Gson provideGson(); } A module to use to...

2.3 The CoordinatorLayout is a container somewhat similar to FrameLayout but with extra capabilities, it is called super-powered FrameLayout in the official documentation. By attaching a CoordinatorLayout.Behavior to a direct child of CoordinatorLayout, you’ll be able to intercept touch events, wi...

java.util.Date to java.sql.Date conversion is usually necessary when a Date object needs to be written in a database. java.sql.Date is a wrapper around millisecond value and is used by JDBC to identify an SQL DATE type In the below example, we use the java.util.Date() constructor, that creates a D...

This code compiles: Integer arg = null; int x = arg; But it will crash at runtime with a java.lang.NullPointerException on the second line. The problem is that a primitive int cannot have a null value. This is a minimalistic example, but in practice it often manifests in more sophisticated f...

Sometimes a RecyclerView will need to use several types of Views to be displayed in the list shown in the UI, and each View needs a different layout xml to be inflated. For this issue, you may use different ViewHolders in single Adapter, by using a special method in RecyclerView - getItemViewType(i...

When adding content from sources outside your domain, or from the local file system the canvas is marked as tainted. Attempt to access the pixel data, or convert to a dataURL will throw a security error. vr image = new Image(); image.src = "file://myLocalImage.png"; image.onload = funct...

At run time the following would display a list of url in your console and continue computation payload = [{url:..., title:...}, {url=..., title=...}] main = payload |> List.map .url -- only takes the url |> Debug.log " My list of URLs" -- pass the url...