Tutorial by Examples: t

Newline character is not consumed in typical scanf() call

When this program #include <stdio.h> #include <string.h> int main(void) { int num = 0; char str[128], *lf; scanf("%d", &num); fgets(str, sizeof(str), stdin); if ((lf = strchr(str, '\n')) != NULL) *lf = '\0'; printf("%d \"%s\&...

C Language • Common pitfalls

Asset packages

Asset Packages (with the file format of .unitypackage) are a commonly used way of distributing Unity projects to other users. When working with peripherals that have their own SDKs (eg. Oculus), you may be asked to download and import one of these packages. Importing a .unitypackage To import a pa...

unity3d • How to use asset packages

Adding a NOT NULL constraint to existing data

Say you want to add a foreign key company_id to the users table, and you want to have a NOT NULL constraint on it. If you already have data in users, you will have to do this in multiple steps. class AddCompanyIdToUsers < ActiveRecord::Migration def up # add the column with NULL allowed ...

Ruby on Rails • ActiveRecord Migrations

Minimal Chart Example

Depending on the version of Chart.JS you are using (the current one being 2.X), the syntax is different to create a minimal example of a bar chart (JSFiddle Demo for 2.X). Chart.js 2.X <html> <body> <canvas id="myChart" width="400" height="400&...

chart.js • Getting started with chart.js

Encoding to a String

str := base64.StdEncoding.EncodeToString([]byte(`foo bar`)) fmt.Println(str) // Output: Zm9vIGJhcg== Playground

Go • Base64 Encoding

Decoding a String

decoded, err := base64.StdEncoding.DecodeString(`biws`) if err != nil { log.Fatal(err) } fmt.Printf("%s", decoded) // Output: n,, Playground

Go • Base64 Encoding

Adding objects

Anything that needs to happen with data in an IndexedDB database happens in a transaction. There are a few things to note about transactions that are mentioned in the Remarks section at the bottom of this page. We'll use the database we set up in Opening a database. // Create a new readwrite (sinc...

JavaScript • IndexedDB

Retrieving data

Anything that needs to happen with data in an IndexedDB database happens in a transaction. There are a few things to note about transactions that are mentioned in the Remarks section at the bottom of this page. We'll use the database we set up in Opening a database. // Create a new transaction, we...

JavaScript • IndexedDB

Initial project workflow

Create a new project dotnet new -l f# Restore any packages listed in project.json dotnet restore A project.lock.json file should be written out. Execute the program dotnet run The above will compile the code if required. The output of the default project created by dotnet new -l f# con...

F# • F# on .NET Core

Espresso custom matchers

Espresso by default has many matchers that help you find views that you need to do some checks or interactions with them. Most important ones can be found in the following cheat sheet: https://google.github.io/android-testing-support-library/docs/espresso/cheatsheet/ Some examples of matchers are...

Android • Testing UI with Espresso

Presenting UI with setContentView

Activity class takes care of creating a window for you in which you can place your UI with setContentView. There are three setContentView methods: setContentView(int layoutResID) - Set the activity content from a layout resource. setContentView(View view) - Set the activity content to an explic...

Android • Activity

Natural (comparable) vs explicit (comparator) sorting

There are two Collections.sort() methods: One that takes a List<T> as a parameter where T must implement Comparable and override the compareTo() method that determines sort order. One that takes a List and a Comparator as the arguments, where the Comparator determines the sort order. ...

Java Language • Comparable and Comparator

Adding/Removing an Observer with a Block

Instead of adding an observer with a selector, a block can be used: id testObserver = [[NSNotificationCenter defaultCenter] addObserverForName:@"TestNotification" object:nil ...

iOS • NSNotificationCenter

Optimization Example (golden)

The 'Golden' method minimizes a unimodal function by narrowing the range in the extreme values import numpy as np from scipy.optimize import _minimize from scipy import special import matplotlib.pyplot as plt x = np.linspace(0, 10, 500) y = special.j0(x) optimize.minimize_scalar(special.j0,...

scipy • How to write a Jacobian function for optimize.minimize

Optimization Example (Brent)

Brent's method is a more complex algorithm combination of other root-finding algorithms; however, the resulting graph isn't much different from the graph generated from the golden method. import numpy as np import scipy.optimize as opt from scipy import special import matplotlib.pyplot as plt ...

scipy • How to write a Jacobian function for optimize.minimize

Rosenbrock function

Think this could example could be better but you get the gist import numpy as np from scipy.optimize import _minimize from scipy import special import matplotlib.pyplot as plt from matplotlib import cm from numpy.random import randn x, y = np.mgrid[-2:2:100j, -2:2:100j] plt.pcolor(x, y, op...

scipy • How to write a Jacobian function for optimize.minimize

Cross Platform OpenGL context creation (using SDL2)

Creating a Window with OpenGL context (extension loading through GLEW): #define GLEW_STATIC #include <GL/glew.h> #include <SDL2/SDL.h> int main(int argc, char* argv[]) { SDL_Init(SDL_INIT_VIDEO); /* Initialises Video Subsystem in SDL */ /* Setting up OpenGL version a...

opengl • Getting started with opengl

has_secure_token

Create User Model # Schema: User(token:string, auth_token:string) class User < ActiveRecord::Base has_secure_token has_secure_token :auth_token end Now when you create a new user a token and auth_token are automatically generated user = User.new user.save user.token # => "p...

Ruby on Rails • User Authentication in Rails

Use assert

Matlab allows some very trivial mistakes to go by silently, which might cause an error to be raised much later in the run - making debugging hard. If you assume something about your variables, validate it. function out1 = get_cell_value_at_index(scalar1,cell2) assert(isscalar(scalar1),'1st input ...

MATLAB Language • MATLAB Best Practices

What is POSIX?

POSIX stands for "Portable Operating System Interface" and defines a set of standards to provide compatibility between different computing platforms. The current version of the standard is IEEE 1003.1 2016 and can be accessed from the OpenGroup POSIX specification. Previous versions incl...

POSIX • Getting started with POSIX