Tutorial by Examples: r

When you document your code with @doc, you can supply code examples like so: # myproject/lib/my_module.exs defmodule MyModule do @doc """ Given a number, returns `true` if the number is even, otherwise `false`. ## Example iex> MyModule.even?(2) true ie...

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...

Initializing std::array<T, N>, where T is a scalar type and N is the number of elements of type T If T is a scalar type, std::array can be initialized in the following ways: // 1) Using aggregate-initialization std::array<int, 3> a{ 0, 1, 2 }; // or equivalently std::array<int, 3...

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 ...

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 ...

Bad Example: var location = dbContext.Location .Where(l => l.Location.ID == location_ID) .SingleOrDefault(); return location; Since the above code is simply returning an entity without modifying or adding it, we can avoid tracking cost. Good Ex...

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...

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...

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...

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...

The __info__/1 function takes one of the following atoms: :functions - Returns a keyword list of public functions along with their arities :macros - Returns a keyword list of public macros along with their arities To list the Kernel module’s functions: iex> Kernel.__info__ :functions [...

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...