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pp:2026:scala:l05 [2026/03/26 07:23] ldaniel given conversions la 5.1.3 |
pp:2026:scala:l05 [2026/05/02 21:34] (current) cosmin.asavoae |
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| </code> | </code> | ||
| - | **5.1.3** Write a function which takes an Int and converts it to a Nat. Write the opposite function, which takes a Nat and converts it to Int. | + | **5.1.3** Write a function which takes an Int and converts it to a Nat. Write the inverse function, which takes a Nat and converts it to Int. |
| <code scala> | <code scala> | ||
| def toNat(x: Int): Nat = ??? | def toNat(x: Int): Nat = ??? | ||
| Line 31: | Line 31: | ||
| <hidden Automatic conversions> | <hidden Automatic conversions> | ||
| <code scala> | <code scala> | ||
| - | given nat2Int: Conversion[Nat, Int] with | + | given nat2Int: Conversion[Nat, Int] = toInt |
| - | def apply(x: Nat): Int = toInt(x) | + | |
| - | given int2Nat: Conversion[Int, Nat] with | + | given int2Nat: Conversion[Int, Nat] = toNat |
| - | def apply(x: Int): Nat = toNat(x) | + | |
| // the second conversion is used to cast params from Int to Nat | // the second conversion is used to cast params from Int to Nat | ||
| Line 98: | Line 96: | ||
| } | } | ||
| - | '\n' + printTree(this) | + | "\n" + printTree(this) |
| } | } | ||
| } | } | ||
| + | def leaf_node(value : Int) : BinaryTree = Node(TVoid, value, TVoid) | ||
| </code> | </code> | ||
| Line 117: | Line 116: | ||
| </code> | </code> | ||
| - | **5.3.2** Write a function which takes a BinaryTree and returns the number of nodes in its subtree. | + | **5.3.2** Write a function which takes a BinaryTree and returns the total number of nodes in it. |
| <code scala> | <code scala> | ||
| - | def subtree(tree: BinaryTree): Int = ??? | + | def size(tree: BinaryTree): Int = ??? |
| </code> | </code> | ||
| Line 132: | Line 131: | ||
| </code> | </code> | ||
| - | **(!) 5.3.5** Write a function which takes two BinaryTree and tries to assign the second tree as a child of the first. It should return a "container" of a BinaryTree . | + | **(!) 5.3.5** Write a function which takes two BinaryTree and tries to assign the second tree as a child of the first. It should return a "container" of a BinaryTree. The append is successful if the second tree can become a direct child of the first tree's root. |
| <code scala> | <code scala> | ||
| def append(tree1: BinaryTree, tree2: BinaryTree): Option[BinaryTree] = ??? | def append(tree1: BinaryTree, tree2: BinaryTree): Option[BinaryTree] = ??? | ||
| Line 140: | Line 139: | ||
| Given the following implementation of expressions, solve the next few exercises. | Given the following implementation of expressions, solve the next few exercises. | ||
| <code scala> | <code scala> | ||
| - | trait Expr | + | sealed trait Expr |
| case class Atom(a: Int) extends Expr | case class Atom(a: Int) extends Expr | ||
| case class Add(e1: Expr, e2: Expr) extends Expr | case class Add(e1: Expr, e2: Expr) extends Expr | ||
| Line 162: | Line 161: | ||
| <hidden> | <hidden> | ||
| - | If you work outside of worksheets, you can define the trait as: | + | <del>If you work outside of worksheets</del>, you can define the trait as: |
| <code scala> | <code scala> | ||
| sealed trait Expr { | sealed trait Expr { | ||
| def + (that: Expr): Expr = Add(this, that) | def + (that: Expr): Expr = Add(this, that) | ||
| - | def * (that: Expr): Expr = Mul(this, that) | + | def * (that: Expr): Expr = Mult(this, that) |
| } | } | ||
| case class Atom(a: Int) extends Expr | case class Atom(a: Int) extends Expr | ||
| Line 190: | Line 189: | ||
| will be represented by the list ''[ [1,2,3],[4,5,6],[7,8,9] ]''. | will be represented by the list ''[ [1,2,3],[4,5,6],[7,8,9] ]''. | ||
| + | <hidden Scala definition> | ||
| + | In Scala, we can define this matrix like this: | ||
| + | <code scala> | ||
| + | val mat = List(List(1, 2, 3), List(4, 5, 6), List(7,8,9)) | ||
| + | </code> | ||
| + | Or.. if you like Cons and Nil, like this: | ||
| + | <code scala> | ||
| + | val mat2 = (1::2::3::Nil)::(4::5::6::Nil)::(7::8::9::Nil)::Nil | ||
| + | </code> | ||
| + | </hidden> | ||
| To make signatures more legible, add the //type alias// to your code: | To make signatures more legible, add the //type alias// to your code: | ||
| <code scala> type Matrix = List[List[Int]] </code> | <code scala> type Matrix = List[List[Int]] </code> | ||