Tutorial by Examples: p

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...

{ 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). "...

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...

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 ...

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 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...

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...

Inline expansion can be disabled with the go:noinline pragma. For example, if we build the following simple program: package main func printhello() { println("Hello") } func main() { printhello() } we get output that looks like this (trimmed for readability): $ go ...

Debugging with IEx.pry/0 is quite simple. require IEx in your module Find the line of code you want to inspect Add IEx.pry after the line Now start your project (e.g. iex -S mix). When the line with IEx.pry/0 is reached the program will stop and you have the chance to inspect. It is like a ...

This example shows how to configure multiple environments with different Dependency Injection configuration and separate middlewares in one Startup class. Alongside of public void Configure(IApplicationBuilder app) and public void ConfigureServices(IServiceCollection services) methods one can use C...

Detailed instructions on getting websphere-mq set up or installed.

Use keyword lists for 'options'-style parameters that contains multiple key-value pairs: def myfunc(arg1, opts \\ []) do # Function body end We can call the function above like so: iex> myfunc "hello", pizza: true, soda: false which is equivalent to: iex> myfunc("he...

class Vector { double x double y } def points = [ new Vector(x: 10, y: -5), new Vector(x: -17.5, y: 3), new Vector(x: -3.3, y: -1) ] assert points*.x == [10, -17.5, -3.3] Note: The * is optional. We could also write the above statement as in the below line and Groov...

To run a command in a shell, in which you required buffered output (i.e. it is not a stream), use child_process.exec. For example, if you wanted to run the command cat *.js file | wc -l, with no options, that would look like this: const exec = require('child_process').exec; exec('cat *.js file | w...

If you are looking to run a file, such as an executable, use child_process.execFile. Instead of spawning a shell like child_process.exec would, it will directly create a new process, which is slightly more efficient than running a command. The function can be used like so: const execFile = require(...

Programs throw errors when for instance wrong input is given. Because of this, one needs to make sure that an error is thrown when actual wrong input is given. Because of that we need to check for an exact exception, for this example we will use the following exception: class WrongInputException(Ex...