Tutorial by Examples: io

Often you need to change the way a set of data is structured and manipulate certain values. In the example below we got a collection of books with an attached discount amount. But we much rather have a list of books with a price that's already discounted. $books = [ ['title' => 'The Pragma...

Collections also provide you with an easy way to do simple statistical calculations. $books = [ ['title' => 'The Pragmatic Programmer', 'price' => 20], ['title' => 'Continuous Delivery', 'price' => 30], ['title' => 'The Clean Coder', 'price' => 10], ] $min = col...

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...

Simple recursion Using recursion and the ternary conditional operator, we can create an alternative implementation of the built-in factorial function: myfactorial(n) = n == 0 ? 1 : n * myfactorial(n - 1) Usage: julia> myfactorial(10) 3628800 Working with trees Recursive functions are o...

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...

Functions are objects in Julia. Like any other objects, they can be passed as arguments to other functions. Functions that accept functions are known as higher-order functions. For instance, we can implement an equivalent of the standard library's foreach function by taking a function f as the firs...

Arrow syntax Anonymous functions can be created using the -> syntax. This is useful for passing functions to higher-order functions, such as the map function. The below function computes the square of each number in an array A. squareall(A) = map(x -> x ^ 2, A) An example of using this fu...

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...

static void testNumericPromotion() { char char1 = 1, char2 = 2; short short1 = 1, short2 = 2; int int1 = 1, int2 = 2; float float1 = 1.0f, float2 = 2.0f; // char1 = char1 + char2; // Error: Cannot convert from int to char; // short1 = short1 + short2; // Err...

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...

static void Main(string[] args) { string url = "www.stackoverflow.com"; var pingTask = PingUrlAsync(url); Console.WriteLine($"Waiting for response from {url}"); Task.WaitAll(pingTask); Console.WriteLine(pingTask.Re...

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...

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...

A pointer to base class can be converted to a pointer to derived class using static_cast. static_cast does not do any run-time checking and can lead to undefined behaviour when the pointer does not actually point to the desired type. struct Base {}; struct Derived : Base {}; Derived d; Base* p1 ...

The shell provisioner runs a shell script when provisioning. $setup = <<SETUP # You can write your shell script between here ... sudo echo "Hello, World!" > /etc/motd.tail # ... and here. SETUP Vagrant.configure("2") do |config| config.vm.box = "ubuntu/tr...

A class, functions as a template that defines the basic characteristics of a particular object. Here's an example: class Person(object): """A simple class.""" # docstring species = "Homo Sapiens" ...

By default the Large Object Heap is not compacted unlike the classic Object Heap which can lead to memory fragmentation and further, can lead to OutOfMemoryExceptions Starting with .NET 4.5.1 there is an option to explicitly compact the Large Object Heap (along with a garbage collection): GCSettin...

Prolog doesn't have iteration, but all iteration can be rewritten using recursion. Recursion appears when a predicate contains a goal that refers to itself. When writing such predicates in Prolog, a standard recursive pattern always has at least two parts: Base (non-recursive) clause: Typically...