Differences
This shows you the differences between two versions of the page.
| Both sides previous revision Previous revision Next revision | Previous revision | ||
|
pp:2026:scala:l03 [2026/03/09 23:15] ldaniel |
pp:2026:scala:l03 [2026/03/26 07:30] (current) ldaniel sealed la binaryTree |
||
|---|---|---|---|
| Line 11: | Line 11: | ||
| This definition has already been implemented in Scala, as shown below. Please copy-paste this definition in your worksheet. | This definition has already been implemented in Scala, as shown below. Please copy-paste this definition in your worksheet. | ||
| <code scala> | <code scala> | ||
| - | trait IList | + | sealed trait IList |
| case object Void extends IList | case object Void extends IList | ||
| case class Cons(x: Int, xs: IList) extends IList | case class Cons(x: Int, xs: IList) extends IList | ||
| </code> | </code> | ||
| + | ''! Hint:'' We use the keyword ''sealed'' to specify that all posible implementations of a trait are in the current file (here, Void and Cons for IList). | ||
| **3.1.1.** Consider the following axioms for the operator ''isEmpty''. | **3.1.1.** Consider the following axioms for the operator ''isEmpty''. | ||
| Line 94: | Line 95: | ||
| The binary tree type definition for Scala is given below. Please copy-paste this definition in your Main.scala file from your laboratory project, in order for printTree to work properly. Call print from the function main and click the "run" text above the definition of main to see the result in terminal. | The binary tree type definition for Scala is given below. Please copy-paste this definition in your Main.scala file from your laboratory project, in order for printTree to work properly. Call print from the function main and click the "run" text above the definition of main to see the result in terminal. | ||
| <code scala> | <code scala> | ||
| - | trait BinaryTree { | + | sealed trait BinaryTree { |
| override def toString: String = super.toString: String | override def toString: String = super.toString: String | ||
| } | } | ||
| Line 146: | Line 147: | ||
| </code> | </code> | ||
| - | **3.2.1.** Implement ''flatten'' that squashes the tree traversed in preorder into a list: | + | **3.2.2.** Implement ''flatten'' that squashes the tree traversed in preorder into a list: |
| <code scala> | <code scala> | ||
| def flatten(tree: BinaryTree): List[Int] = ??? | def flatten(tree: BinaryTree): List[Int] = ??? | ||
| </code> | </code> | ||
| - | **3.2.2.** Define the function ''tmap'' which is the Tree a correspondent to map::(a→b) → [a] → [b]. | + | **3.2.3.** Define the function ''tmap'' which is the Tree a correspondent to map::(a→b) → [a] → [b]. |
| <code scala> | <code scala> | ||
| def tmap(f: Int => Int, tree: BinaryTree) : BinaryTree = ??? | def tmap(f: Int => Int, tree: BinaryTree) : BinaryTree = ??? | ||
| </code> | </code> | ||
| - | **3.2.3.** ! Define the function ''tfoldr'', equivalent of foldr for trees: foldr :: (a -> b -> b) -> b -> Tree a -> b | + | **3.2.4.** ! Define the function ''tfoldr'', equivalent of foldr for trees: foldr :: (a -> b -> b) -> b -> Tree a -> b |
| <code scala> | <code scala> | ||
| def tfoldr[B](f: (Int, B) => B, acc: B, tree: BinaryTree): B = ??? | def tfoldr[B](f: (Int, B) => B, acc: B, tree: BinaryTree): B = ??? | ||
| </code> | </code> | ||
| - | **3.2.4.** ! Implement the ''flattening'' function using tfoldr. The order of squashing the tree does not necessarily need to match the previous exercise: | + | **3.2.5.** ! Implement the ''flattening'' function using tfoldr. The order of squashing the tree does not necessarily need to match the previous exercise: |
| <code scala> | <code scala> | ||
| def flattening(tree: BinaryTree): List[Int] = ??? | def flattening(tree: BinaryTree): List[Int] = ??? | ||