Scala Implicits and Type Classes

Question 1

Which keyword is used to define an implicit value in Scala 2?

Accepted Answer

implicit

Answer

given

Answer

using

Answer

infer

Question 2

In Scala 3, which keyword replaces `implicit val` for defining implicit instances?

Accepted Answer

given

Answer

implicit

Answer

using

Answer

auto

Question 3

What best describes a type class in Scala?

Accepted Answer

A pattern using traits and implicits to achieve ad-hoc polymorphism

Answer

A class that extends multiple traits simultaneously

Answer

A class defined with the `type` keyword

Answer

A sealed abstract class with bounded type parameters

Question 4

Which of the following correctly declares an implicit parameter in Scala 2?

Accepted Answer

def foo(implicit x: Int): Unit

Answer

def foo(given x: Int): Unit

Answer

def foo[implicit x: Int]: Unit

Answer

def foo(@implicit x: Int): Unit

Question 5

What happens when the Scala compiler cannot find a required implicit value in scope?

Accepted Answer

It produces a compile-time error

Answer

It uses null as the default value

Answer

It throws a runtime NullPointerException

Answer

It searches the runtime classpath for the implicit

Question 6

What is an implicit conversion in Scala?

Accepted Answer

A method marked `implicit` that the compiler applies automatically to convert one type to another

Answer

A conversion that occurs automatically at JVM bytecode level

Answer

A conversion requiring an explicit cast with `asInstanceOf`

Answer

A built-in conversion between primitive types and their boxed counterparts

Question 7

What is the purpose of the `implicitly[T]` method in Scala 2?

Accepted Answer

To summon an implicit value of type T from the current scope

Answer

To mark a method as implicit

Answer

To convert a value to type T implicitly

Answer

To define an implicit class wrapping type T