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pp:2025:scala:l04 [2025/03/19 20:41]
cata_chiru 		pp:2025:scala:l04 [2025/03/19 20:51] (current)
cata_chiru
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 </​code>​ </​code>​
  
-**4.1.2.** Write a function which returns the first ''​n''​ elements from a given list. The function should **not** be implemented as tail-recursive. +**4.1.2.** Write a function which takes a predicate ''​p:​ Int => Boolean'',​ a list ''​l''​ and returns a sublist of ''​l''​ containing those elements for which ''​p''​ is true. The function should be **curried**.
- +
-<code scala> +
-def take(n: Int, l: List[Int]): List[Int] = ??? +
-//​take(3,​List(1,​2,​3,​4,​5)) = List(1,​2,​3) +
-</​code>​ +
- +
-**4.1.3.** Write a function which //drops// the first ''​n''​ elements from a given list. +
- +
-<code scala> +
-def drop(n: Int, l: List[Int]): List[Int] = ??? +
-//​drop(3,​List(1,​2,​3,​4,​5)) = List(4,5) +
-</​code>​ +
- +
-**4.1.4.** Write a function which takes a predicate ''​p:​ Int => Boolean'',​ a list ''​l''​ and returns a sublist of ''​l''​ containing those elements for which ''​p''​ is true. The function should be **curried**.+
  
 <code scala> <code scala>
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 </​code>​ </​code>​
  
-**4.1.5.** Write a function which uses a predicate to partition (split) a list.+**4.1.3.** Write a function which uses a predicate to partition (split) a list.
 <code scala> <code scala>
 def part(p: Int => Boolean)(l: List[Int]): (List[Int], List[Int]) = ??? def part(p: Int => Boolean)(l: List[Int]): (List[Int], List[Int]) = ???
 // part(_%2 == 0)(List(1,​2,​3,​4,​5,​6)) = (List(2,​4,​6),​List(1,​3,​5)) // part(_%2 == 0)(List(1,​2,​3,​4,​5,​6)) = (List(2,​4,​6),​List(1,​3,​5))
-</​code>​ 
- 
-**4.1.6.** Write a function that reverses the elements of a list. Use a ''​fold''​ function (determine if it should be right or left). 
-<code scala> 
-def rev(l: List[Int]): List[Int] = ??? 
-// rev(List(1,​2,​3,​4,​5,​6)) = List(6,​5,​4,​3,​2,​1) 
 </​code>​ </​code>​
  
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 </​code>​ </​code>​
  
-**4.2.5.** Implement a function that return ​the domains without the dot (ex. ''​gmail''​).+**4.2.5.** Implement a function that returns ​the domains without the dot (ex. ''​gmail''​).
 <code scala> <code scala>
 def domains(list:​ List[Str]): List[Str] = ??? def domains(list:​ List[Str]): List[Str] = ???
 </​code>​ </​code>​
- 
- 
- 
  
 ==== 4.3. Gradebooks ==== ==== 4.3. Gradebooks ====