It is predominately used for Dependency Injection, such as in the Cake Pattern. There exists a great article covering many different forms of dependency injection in Scala, including the Cake Pattern. If you Google “Cake Pattern and Scala”, you’ll get many links, including presentations and videos. For now, here is a link to another question. … Read more
Types of Implicits Implicits in Scala refers to either a value that can be passed “automatically”, so to speak, or a conversion from one type to another that is made automatically. Implicit Conversion Speaking very briefly about the latter type, if one calls a method m on an object o of a class C, and … Read more
I divide the operators, for the purpose of teaching, into four categories: Keywords/reserved symbols Automatically imported methods Common methods Syntactic sugars/composition It is fortunate, then, that most categories are represented in the question: -> // Automatically imported method ||= // Syntactic sugar ++= // Syntactic sugar/composition or common method <= // Common method _._ // … Read more
In the usual encoding an enumerator is essentially a StepT[E, F, ?] ~> F[StepT[E, F, ?]]. If you try to write a generic method converting this type into a Step[E, G, ?] ~> G[Step[E, G, ?]] given an F ~> G, you’ll quickly run into an issue: you need to “lower” a Step[E, G, A] … Read more
Case classes can be seen as plain and immutable data-holding objects that should exclusively depend on their constructor arguments. This functional concept allows us to use a compact initialization syntax (Node(1, Leaf(2), None))) decompose them using pattern matching have equality comparisons implicitly defined In combination with inheritance, case classes are used to mimic algebraic datatypes. … Read more
The ones I can think of are Existential types def foo(l: List[Option[_]]) = … Higher kinded type parameters case class A[K[_],T](a: K[T]) Ignored variables val _ = 5 Ignored parameters List(1, 2, 3) foreach { _ => println(“Hi”) } Ignored names of self types trait MySeq { _: Seq[_] => } Wildcard patterns Some(5) match … Read more
Groovy is a dynamically typed language, whose syntax is very close to Java, with a number of syntax improvements that allow for lighter code and less boilerplate. It can run through an interpreter as well as being compiled, which makes it good for fast prototyping, scripts, and learning dynamic languages without having to learn a … Read more
tl;dr class C defines a class, just as in Java or C++. object O creates a singleton object O as instance of some anonymous class; it can be used to hold static members that are not associated with instances of some class. object O extends T makes the object O an instance of trait T; … Read more
I hope it’s not a “suicide note”, but I can see your point. You hit on what is at the same time both a strength and a problem of Scala: its extensibility. This lets us implement most major functionality in libraries. In some other languages, sequences with something like map or collect would be built … Read more