Scala Implicits and Type Classes 3

Question 1

In Scala 3, what is `summon[T]` equivalent to in Scala 2?

Accepted Answer

implicitly[T]

Answer

explicitly[T]

Answer

manifest[T]

Answer

typeOf[T]

Question 2

Which syntax correctly defines a Scala 3 extension method that adds `double` to `Int`?

Accepted Answer

extension (n: Int) def double: Int = n * 2

Answer

implicit class RichInt(n: Int) { def double: Int = n * 2 }

Answer

def double(implicit n: Int): Int = n * 2

Answer

given (n: Int) def double: Int = n * 2

Question 3

What is 'implicit ambiguity' in Scala?

Accepted Answer

When two or more equally valid implicits exist in scope for the same type, causing a compile error

Answer

When an implicit value has an ambiguous or unclear name

Answer

When an implicit parameter also has a default value

Answer

When an implicit conversion could apply to more than one target type

Question 4

What does the type constraint `implicit ev: A =:= B` assert in Scala?

Accepted Answer

That types A and B are exactly the same type

Answer

That type A is a subtype of B

Answer

That A can be implicitly converted to B

Answer

That A and B share the same companion object

Question 5

What is the Magnet pattern in Scala?

Accepted Answer

A design pattern using implicits to simulate method overloading on a single method

Answer

A pattern for generating random magnetized test data

Answer

A pattern for creating lazy singleton instances via implicit lazy val

Answer

A pattern for attracting implicit conversions from companion objects

Question 6

What is Scala's `Numeric[T]` type class used for?

Accepted Answer

Providing arithmetic and numeric operations for generic code over any numeric type

Answer

Converting strings to numeric types at runtime

Answer

Defining custom literal syntax for number types

Answer

Parsing numeric tokens in parser combinators

Question 7

In Scala 3, which import syntax correctly brings all `given` instances from object `MyInstances` into scope?

Accepted Answer

import MyInstances.given

Answer

import MyInstances._

Answer

import MyInstances.*

Answer

using MyInstances._