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4. Lists in Scala
4.1. Common list operations
4.1.1.* Write a function which returns true if a list of integers has at least k elements. Use patterns.
<code scala>
def atLeastk(k: Int, l: List[Int]): Boolean =
if (k == 0) ???
else ???
}
</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.
<code scala>
def take(n: Int, l: List[Int]): List[Int] = ???
take(3,List(1,2,3,4,5)) = 3
</code>
4.1.3. Write a function which drops the first n
elements from a given list. The function should not be implemented as tail-recursive.
<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>
def takeP(p: Int ⇒ Boolean)(l: List[Int]): List[Int] = ???
takeP(_%2 == 0)(List(1,2,3,4,5,6)) = List(2,4,6)
</code>
4.1.5. Write a function which uses a predicate to partition (split) a list.
<code scala>
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))
</code>