pattern matching

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Pattern Matching of Sealed Classes

pattern matching

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@switch annotatition

pattern matching

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What will be printed into the console? val Constant = 'Q' def tokenMe(ch: Char) = (ch: @switch) match { case ' ' | '\t' | '\n' => 1 case 'A' | 'Z' | '$' => 2 case '5' | Constant => 3 case _ => 4 } println(tokenMe('5'))

pattern matching

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Examine the next Scala match expression. What will be the result of pattern matching of the list? val x = List(1, 2, 3, 4, 5) match { case Cons(x, Cons(2, Cons(4, _))) => x case Nil => 42 case Cons(x, Cons(y, Cons(3, Cons(4, _)))) => x + y case Cons(h, t) => h + sum(t) case _ => 101 } Assuming the following code is available for your reference sealed trait List[+A] case object Nil extends List[Nothing] case class Cons[+A](head: A, tail: List[A]) extends List[A]

pattern matching

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Take a look at the implementation of the following function, select the correct result: def someFunction[A](list: List[A]): List[A] = list match { case Nil => sys.error("empty list") case Cons(_, t) => t } someFunction(List(1, 2, 3)) Assuming the following code is available for your reference sealed trait List[+A] case object Nil extends List[Nothing] case class Cons[+A](head: A, tail: List[A]) extends List[A]

pattern matching

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Take a look at the implementation of the following function, select the correct result: def someFunction[A](list: List[A]): List[A] = list match { case Nil => sys.error("empty list") case Cons(_, t) => t } someFunction(List(1)) Assuming the following code is available for your reference sealed trait List[+A] case object Nil extends List[Nothing] case class Cons[+A](head: A, tail: List[A]) extends List[A]

pattern matching

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Take a look at the implementation of the following function, select the correct result: def someFunction[A](l: List[A], h: A): List[A] = l match { case Nil => sys.error("empty list") case Cons(_, t) => Cons(h, t) } someFunction(List(1, 2, 3), 3) Assuming the following code is available for your reference sealed trait List[+A] case object Nil extends List[Nothing] case class Cons[+A](head: A, tail: List[A]) extends List[A]

pattern matching

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Given drop function implemented with pattern matching, what is the result of the code execution? def drop[A](l: List[A], n: Int): List[A] = if (n <= 0) l else l match { case Nil => Nil case Cons(_, t) => drop(t, n - 1) } drop(List(1, 2, 3), 1) Assuming the following code is available for your reference sealed trait List[+A] case object Nil extends List[Nothing] case class Cons[+A](head: A, tail: List[A]) extends List[A]

pattern matching

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Select correct implementation of drop function, so that following expression is true. drop(List(1, 2, 3), 1) == List(2,3) Assuming the following code is available for your reference sealed trait List[+A] case object Nil extends List[Nothing] case class Cons[+A](head: A, tail: List[A]) extends List[A]

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What is the result of code execution? def drop[A](l: List[A], n: Int): List[A] = if (n <= 0) l else l match { case Nil => Nil case Cons(_, t) => drop(t, n - 1) } drop(List(1, 2, 3), 0) Assuming the following code is available for your reference sealed trait List[+A] case object Nil extends List[Nothing] case class Cons[+A](head: A, tail: List[A]) extends List[A]

pattern matching