Tutorial by Examples: el

Compare the definition of Free to that of Fix: data Free f a = Return a | Free (f (Free f a)) newtype Fix f = Fix { unFix :: f (Fix f) } In particular, compare the type of the Free constructor with the type of the Fix constructor. Free layers up a functor just like Fix, except ...

The width and height attributes designate the dimensions of the rectangle. These values are in pixels by default The fill value sets the color for the rectangle. If no value for fill is specified, black is used by default <svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="h...

Throughout this example it is assumed that the 'root' object that is being serialized to JSON is an instance of the following class : public class MyJson { }   Example 1 : An example of an instance of MyJson, as is: {} i.e. since the class has no fields, only curly brackets are serialized...

CommandDescriptionzRedraw current line at the top of the window and put the cursor on the first non-blank character on the line.ztLike z but leave the cursor in the same column.z.Redraw current line at the center of the window and put the cursor on the first non-blank character on the line.zzLike z....

If your application is available in different languages, you usually show the current locale in the URL. scope '/(:locale)', locale: /#{I18n.available_locales.join('|')}/ do root 'example#root' # other routes end Your root will be accessible via the locales defined in I18n.available_l...

A self reference can be useful to build a hierarchical tree. This can be achieved with add_reference in a migration. class AddParentPages < ActiveRecord::Migration[5.0] def change add_reference :pages, :pages end end The foreign key column will be pages_id. If you want to decide a...

Open Xcode and select Create a new Xcode Project. Now select iOS > Application on the left and Game on the main selection area. Press Next. Write into Product Name the name of your first great game. Into Organization Name the name of your company (or simply your own name). Organisation I...

Let's say you have a User model class User < ActiveRecord::Base end Now to update the first_name and last_name of a user with id = 1, you can write the following code. user = User.find(1) user.update(first_name: 'Kashif', last_name: 'Liaqat') Calling update will attempt to update the gi...

public static void Main(string[] args) { var studentList = new List<Student>(); studentList.Add(new Student("Scott", "Nuke")); studentList.Add(new Student("Vincent", "King")); studentList.Add(new Student("Craig", "Be...

Self-referential association is used to associate a model with itself. The most frequent example would be, to manage association between a friend and his follower. ex. rails g model friendship user_id:references friend_id:integer now you can associate models like; class User < ActiveRecord:...

All collection objects contain a map method that takes a Function as an argument, which must take a single argument. This returns an Iterable backed by the collection. When the Iterable is iterated, each step calls the function with a new element of the collection, and the result of the call becomes...

Swift webview.reload() Objective-C [webview reload];

In case we want to use enum with more information and not just as constant values, and we want to be able to compare two enums. Consider the following example: public enum Coin { PENNY(1), NICKEL(5), DIME(10), QUARTER(25); private final int value; Coin(int value){ this....

The following code can be entered in a Tcl shell (tclsh), or into a script file and run through a Tcl shell: puts "Hello, world!" It gives the string argument Hello, world! to the command puts. The puts command writes its argument to standard out (your terminal in interactive mode) an...

C++11 The type std::conditional in the standard library header <type_traits> can select one type or the other, based on a compile-time boolean value: template<typename T> struct ValueOrPointer { typename std::conditional<(sizeof(T) > sizeof(void*)), T*, T>::type vop; }...

Passing a context with a timeout (or with a cancel function) to a long running function can be used to cancel that functions work: ctx, _ := context.WithTimeout(context.Background(), 200*time.Millisecond) for { select { case <-ctx.Done(): return ctx.Err() default: ...

3.0 let someString = " Swift Language \n" let trimmedString = someString.stringByTrimmingCharactersInSet(NSCharacterSet.whitespaceAndNewlineCharacterSet()) // "Swift Language" Method stringByTrimmingCharactersInSet returns a new string made by removing from both ends of t...

Early Bound (with a reference to Microsoft Scripting Runtime) Sub EnumerateFilesAndFolders( _ FolderPath As String, _ Optional MaxDepth As Long = -1, _ Optional CurrentDepth As Long = 0, _ Optional Indentation As Long = 2) Dim FSO As Scripting.FileSystemObject Set ...

Create a model (lets call it User) by running: $ rails g model User which will generate the file app/models/user.rb: class User include Mongoid::Document end This is all you need to have a model (albeit nothing but an id field). Unlike ActiveRecord, there is no migration files. All the...

As per the Mongoid Documentation, there are 16 valid field types: Array BigDecimal Boolean Date DateTime Float Hash Integer BSON::ObjectId BSON::Binary Range Regexp String Symbol Time TimeWithZone To add a field (let's call it name and have it be a String), add this to your mode...