Tutorial by Examples: gas

A traversal can be run in the opposite direction with the help of the Backwards applicative functor, which flips an existing applicative so that composed effects take place in reversed order. newtype Backwards f a = Backwards { forwards :: f a } instance Applicative f => Applicative (Backward...

1.8 You can remove a submodule (e.g. the_submodule) by calling: $ git submodule deinit the_submodule $ git rm the_submodule git submodule deinit the_submodule deletes the_submodules' entry from .git/config. This excludes the_submodule from git submodule update, git submodule sync and git ...

docker ps --filter name=myapp_1

Ruby provides several ways to create a String object. The most common way is using single or double quotes to create a "string literal": s1 = 'Hello' s2 = "Hello" The main difference is that double-quoted string literals are a little bit more flexible as they support interpo...

You may need to convert a Stream emitting Optional to a Stream of values, emitting only values from existing Optional. (ie: without null value and not dealing with Optional.empty()). Optional<String> op1 = Optional.empty(); Optional<String> op2 = Optional.of("Hello World");...

String#split splits a String into an Array, based on a delimiter. "alpha,beta".split(",") # => ["alpha", "beta"] An empty String results into an empty Array: "".split(",") # => [] A non-matching delimiter results in an Array...

The most common way to create a Symbol object is by prefixing the string identifier with a colon: :a_symbol # => :a_symbol :a_symbol.class # => Symbol Here are some alternative ways to define a Symbol, in combination with a String literal: :"a_symbol" "a_symbol&quot...

Given a String: s = "something" there are several ways to convert it to a Symbol: s.to_sym # => :something :"#{s}" # => :something

Given a Symbol: s = :something The simplest way to convert it to a String is by using the Symbol#to_s method: s.to_s # => "something" Another way to do it is by using the Symbol#id2name method which is an alias for the Symbol#to_s method. But it's a method that is unique to the...

All java Collection<E>s have stream() and parallelStream() methods from which a Stream<E> can be constructed: Collection<String> stringList = new ArrayList<>(); Stream<String> stringStream = stringList.parallelStream(); A Stream<E> can be created from an arra...

NSAttributedString (and its mutable sibling NSMutableAttributedString) allows you to create strings that are complex in their appearance to the user. A common application is to use this to display a string and adding custom kerning / letter-spacing. This would be achieved as follows (where label ...

traverse_ executes an Applicative action for every element in a Foldable structure. It ignores the action's result, keeping only the side-effects. (For a version which doesn't discard results, use Traversable.) -- using the Writer applicative functor (and the Sum monoid) ghci> runWriter $ trave...

While static constructors are always called before the first usage of a type it's sometimes useful to be able to force them to be called and the RuntimeHelpers class provide an helper for it: using System.Runtime.CompilerServices; // ... RuntimeHelpers.RunClassConstructor(typeof(Foo).TypeHand...

3.0 In Swift 3 there are multiple access-levels. This example uses them all except for open: public struct Car { public let make: String let model: String //Optional keyword: will automatically be "internal" private let fullName: String fileprivate var otherName...

You can use the Integer method to convert a String to an Integer: Integer("123") # => 123 Integer("0xFF") # => 255 Integer("0b100") # => 4 Integer("0555") # => 365 You can also pass a base parameter to the Integer method to c...

A method of a struct that change the value of the struct itself must be prefixed with the mutating keyword struct Counter { private var value = 0 mutating func next() { value += 1 } } When you can use mutating methods The mutating methods are only available on str...

You may add your new Seeder to the DatabaseSeeder class. /** * Run the database seeds. * * @return void */ public function run() { $this->call(UserTableSeeder::class); } To run a database seeder, use the Artisan command php artisan db:seed ...

Database seeds are stored in the /database/seeds directory. You can create a seed using an Artisan command. php artisan make:seed UserTableSeeder Alternatively you can create a new class which extends Illuminate\Database\Seeder. The class must a public function named run().

You can reference models in a seeder. use DB; use App\Models\User; class UserTableSeeder extends Illuminate\Database\Seeder{ public function run(){ # Remove all existing entrie DB::table('users')->delete() ; User::create([ 'name' => 'Admin', ...

While the Java Date class has several constructors, you'll notice that most are deprecated. The only acceptable way of creating a Date instance directly is either by using the empty constructor or passing in a long (number of milliseconds since standard base time). Neither are handy unless you're lo...