Tutorial by Examples: e

Maps and keyword lists have different application. For instance, a map cannot have two keys with the same value and it's not ordered. Conversely, a Keyword list can be a little bit hard to use in pattern matching in some cases. Here's a few use cases for maps vs keyword lists. Use keyword lists wh...

This example shows a simple image cropping function that takes an image and cropping coordinates and returns the cropped image. function cropImage(image, croppingCoords) { var cc = croppingCoords; var workCan = document.createElement("canvas"); // create a canvas workCan.wi...

You can also use the IEx (Interactive Elixir) shell to evaluate expressions and execute code. If you are on Linux or Mac, just type iex on your bash and press enter: $ iex If you are on a Windows machine, type: C:\ iex.bat Then you will enter into the IEx REPL (Read, Evaluate, Print, Loop),...

{ a, b, c } = { "Hello", "World", "!" } IO.puts a # Hello IO.puts b # World IO.puts c # ! # Tuples of different size won't match: { a, b, c } = { "Hello", "World" } # (MatchError) no match of right hand side value: { "Hello",...

The code listing below attempts to classify handwritten digits from the MNIST dataset. The digits look like this: The code will preprocess these digits, converting each image into a 2D array of 0s and 1s, and then use this data to train a neural network with upto 97% accuracy (50 epochs). "...

struct FileAttributes { unsigned int ReadOnly: 1; unsigned int Hidden: 1; }; Here, each of these two fields will occupy 1 bit in memory. It is specified by : 1 expression after the variable names. Base type of bit field could be any integral type (8-bit int to 64-bit int). Using u...

C++11 In C++11, compilers are required to implicitly move from a local variable that is being returned. Moreover, most compilers can perform copy elision in many cases and elide the move altogether. As a result of this, returning large objects that can be moved cheaply no longer requires special ha...

Let's have a basic failing program: #include <iostream> void fail() { int *p1; int *p2(NULL); int *p3 = p1; if (p3) { std::cout << *p3 << std::endl; } } int main() { fail(); } Build it (add -g to include debug info): g++ -g -o m...

class API { public: static API& instance(); virtual ~API() {} virtual const char* func1() = 0; virtual void func2() = 0; protected: API() {} API(const API&) = delete; API& operator=(const API&) = delete; }; class WindowsAPI ...

You can generate a rails migration file from the terminal using the following command: rails generate migration NAME [field[:type][:index] field[:type][:index]] [options] For a list of all the options supported by the command, you could run the command without any arguments as in rails generate ...

Type check: variable.isInstanceOf[Type] With pattern matching (not so useful in this form): variable match { case _: Type => true case _ => false } Both isInstanceOf and pattern matching are checking only the object's type, not its generic parameter (no type reification), except fo...

Let's say we need to add a button for each piece of loadedData array (for instance, each button should be a slider showing the data; for the sake of simplicity, we'll just alert a message). One may try something like this: for(var i = 0; i < loadedData.length; i++) jQuery("#container&q...

create-react-app is a React app boilerplate generator created by Facebook. It provides a development environment configured for ease-of-use with minimal setup, including: ES6 and JSX transpilation Dev server with hot module reloading Code linting CSS auto-prefixing Build script with JS, CSS ...

One problem often seen in code is loading all the data. This will greatly increase the load on the server. Let's say I have a model called "location" that has 10 fields in it, but not all the fields are required at the same time. Let's say I only want the 'LocationName' parameter of that...

Let's take an example of a function which receives two arguments and returns a value indicating their sum: def two_sum(a, b): return a + b By looking at this code, one can not safely and without doubt indicate the type of the arguments for function two_sum. It works both when supplied with ...

The .info file is a static text file for defining and configuring a theme. Each line in the .info file is a key-value pair with the key on the left and the value on the right, with an "equals sign" between them (e.g. name = my_theme). Semicolons are used to comment out a line. Some keys u...

Django comes with a number of builtin management commands, using python manage.py [command] or, when manage.py has +x (executable) rights simply ./manage.py [command] . The following are some of the most frequently used: Get a list of all available commands ./manage.py help Run your Django ser...

The cmath module is similar to the math module, but defines functions appropriately for the complex plane. First of all, complex numbers are a numeric type that is part of the Python language itself rather than being provided by a library class. Thus we don't need to import cmath for ordinary arith...

Erlang modules are available as atoms. For example, the Erlang math module is available as :math: iex> :math.pi 3.141592653589793

Use module_info on Erlang modules you wish to inspect: iex> :math.module_info [module: :math, exports: [pi: 0, module_info: 0, module_info: 1, pow: 2, atan2: 2, sqrt: 1, log10: 1, log2: 1, log: 1, exp: 1, erfc: 1, erf: 1, atanh: 1, atan: 1, asinh: 1, asin: 1, acosh: 1, acos: 1, tanh...