Tutorial by Examples: g

Comparing 2 Arrays with zip

The zip function accepts 2 parameters of type SequenceType and returns a Zip2Sequence where each element contains a value from the first sequence and one from the second sequence. Example let nums = [1, 2, 3] let animals = ["Dog", "Cat", "Tiger"] let numsAndAnimals ...

Swift Language • Arrays

Mixin with variable argument

There are some cases in mixins where there can be single or multiple arguments while using it. Let's take a case of border-radius where there can be single argument like border-radius:4px; or multiple arguments like border-radius:4px 3px 2px 1px;. Traditional with Keyword Arguments mixing will be l...

sass • Mixins

Building with SCons

You can build the cross-platform "Hello World" C++ code, using Scons - A Python-language software construction tool. First, create a file called SConstruct (note that SCons will look for a file with this exact name by default). For now, the file should be in a directory right along your h...

C++ • Build Systems

Inheritance of Singleton Class

Subclassing also Subclasses Singleton Class class Example end Example.singleton_class #=> #<Class:Example> def Example.foo :example end class SubExample < Example end SubExample.foo #=> :example SubExample.singleton_class.superclass #=> #<Class:Example> ...

Ruby Language • Singleton Class

Message Propagation with Singleton Class

Instances never contain a method they only carry data. However we can define a singleton class for any object including an instance of a class. When a message is passed to an object (method is called) Ruby first checks if a singleton class is defined for that object and if it can reply to that mess...

Ruby Language • Singleton Class

Reopening (monkey patching) Singleton Classes

There are three ways to reopen a Singleton Class Using class_eval on a singleton class. Using class << block. Using def to define a method on the object's singleton class directly class Example end Example.singleton_class.class_eval do def foo :foo end end Example.fo...

Ruby Language • Singleton Class

Quoting

In the Tcl language in many cases, no special quoting is needed. These are valid strings: abc123 4.56e10 my^variable-for.my%use The Tcl language splits words on whitespace, so any literals or strings with whitespace should be quoted. There are two ways to quote strings. With braces and with...

tcl • Tcl Language Constructs

Using the revert command to discard unwanted changes.

The revert command allows discarding unwanted uncommitted changes. Reverting changes to a single file. hg revert example.c Reverting all changes. This will discard all changes not just the current directory. hg revert --all hg will output which files were reverted. reverting exa...

mercurial • Common operations

Deleting a derived object via a pointer to a base class that doesn't have a virtual destructor.

class base { }; class derived: public base { }; int main() { base* p = new derived(); delete p; // The is undefined behavior! } In section [expr.delete] §5.3.5/3 the standard says that if delete is called on an object whose static type does not have a virtual destructor: if the...

C++ • Undefined Behavior

Avoiding duplication of code in const and non-const getter methods.

In C++ methods that differs only by const qualifier can be overloaded. Sometimes there may be a need of two versions of getter that return a reference to some member. Let Foo be a class, that has two methods that perform identical operations and returns a reference to an object of type Bar: class ...

C++ • const keyword

Use git send-email with Gmail

Background: if you work on a project like the Linux kernel, rather than make a pull request you will need to submit your commits to a listserv for review. This entry details how to use git-send email with Gmail. Add the following to your .gitconfig file: [sendemail] smtpserver = smtp.googlema...

Git • git send-email

Animate at a specified interval (add a new rectangle every 1 second)

This example adds a new rectangle to the canvas every 1 second (== a 1 second interval) Annotated Code: <!doctype html> <html> <head> <style> body{ background-color:white; } #canvas{border:1px solid red; } </style> <script> window.onload=(functio...

html5-canvas • Animation

Animate an image across the Canvas

This example loads and animates and image across the Canvas Important Hint! Make sure you give your image time to fully load by using image.onload. Annotated Code <!doctype html> <html> <head> <style> body{ background-color:white; } #canvas{border:1px solid re...

html5-canvas • Animation

Runtime Code Generation

<#@ template language="C#" #> //Language of your project <#@ assembly name="System.Core" #> <#@ import namespace="System.Linq" #> <#@ import namespace="System.Text" #> <#@ import namespace="System.Collections.Generic" ...

C# Language • T4 Code Generation

UIColor from an image pattern

You can create a UIColor object using an image pattern by using the UIColor(patternImage:_) method. btn.backgroundColor = UIColor(patternImage: UIImage(named: "image")!)

iOS • UIColor

Working with Varargs parameters

Using varargs as a parameter for a method definition, it is possible to pass either an array or a sequence of arguments. If a sequence of arguments are passed, they are converted into an array automatically. This example shows both an array and a sequence of arguments being passed into the printVar...

Java Language • Varargs (Variable Argument)

Using the Graphics class

Intro The Graphics class allows you to draw onto java components such as a Jpanel, it can be used to draw strings, lines, shapes and images. This is done by overriding the paintComponent(Graphics g) method of the JComponent you are drawing on using the Graphics object received as argument to do the...

swing • Graphics

Drawing images

Images can be drawn onto a JComponent using the drawImage method of class Graphics: loading an image BufferedImage img; try { img = ImageIO.read(new File("stackoverflow.jpg")); } catch (IOException e) { throw new RuntimeException("Could not load image", e); } dr...

swing • Graphics

Rounding Numbers

The round method will round a number up if the first digit after its decimal place is 5 or higher and round down if that digit is 4 or lower. This takes in an optional argument for the precision you're looking for. 4.89.round # => 5 4.25.round # => 4 3.141526.round(1) # => ...

Ruby Language • Numbers

Restrict Number to Min/Max Range

If you need to clamp a number to keep it inside a specific range boundary function clamp(min, max, val) { return Math.min(Math.max(min, +val), max); } console.log(clamp(-10, 10, "4.30")); // 4.3 console.log(clamp(-10, 10, -8)); // -8 console.log(clamp(-10, 10, 12)); // ...

JavaScript • Arithmetic (Math)