All Questions
37 questions
2
votes
3
answers
76
views
List pattern matching add filtering based on case object
I have a list of Male and Female inhabitants to be iterated over.
How to add filtering based on gender to the list pattern matching? (such that countOldManFloor would return 1 only if inhabitants ...
- 3,981
4
votes
2
answers
2k
views
Why use a helper function inside a recursive function?
In the book Functional Programming in Scala, in the context of explaining how recursion is often used in functional programming over imperative iteration, the authors show recursion via a factorial ...
- 3,459
0
votes
2
answers
123
views
Convert Option based linked list to a `List`
What is a nicest way to implement such function
case class Node(prev: Option[Node])
def flatIt(n: Node): List[Node] = ???
val n1 = Node(None)
val n2 = Node(Some(n1))
val n3 = Node(Some(n2))
flatIt(...
- 29.1k
1
vote
1
answer
95
views
Conversion of Looping to Recursive Solution
I have written a method pythagoreanTriplets in scala using nested loops. As a newbie in scala, I am struggling with how can we do the same thing using recursion and use Lazy Evaluation for the ...
- 57
13
votes
1
answer
1k
views
How to reason about stack safety in Scala Cats / fs2?
Here is a piece of code from the documentation for fs2. The function go is recursive. The question is how do we know if it is stack safe and how to reason if any function is stack safe?
import fs2._
/...
- 2,191
-2
votes
1
answer
120
views
Why does the absence of an else block translate to Unit type return for a function?
I noticed there is a type mismatch caused in the line else if(r1 == 0 || divisors.tail.isEmpty || !divisors.tail.contains(r1)){newAcc}. Because there is no else clause to my if ... else if ...
def ...
- 2,743
3
votes
1
answer
166
views
What is a better way to solve this exercise in more Immutable way?
I am trying to solve a problem on HackerRank. I am trying to solve this problem in more functional way (using immutability). I have attempted a solution but I am not fully confident about it.
Here’s ...
- 113
4
votes
2
answers
4k
views
Is this Depth First Search implementation tail recursive now?
I had this function for functionally traversing a graph:
private def dfs(current: RCell, rCellsMovedWithEdges: Vector[RCell], acc: Vector[RCell] = Vector()): Vector[RCell] = {
current.edges....
- 767
12
votes
2
answers
2k
views
How to make tree mapping tail-recursive?
Suppose I have a tree data structure like this:
trait Node { val name: String }
case class BranchNode(name: String, children: List[Node]) extends Node
case class LeafNode(name: String) extends Node
...
- 42.2k
-1
votes
1
answer
71
views
How to identify whether a problem can be solved with Tail-recursion or not in Scala
How can I identify whether a problem statement can be solved with tail recursion or not. Is there any characteristics of a problem by which one can identify that?
0
votes
1
answer
234
views
Scala Polymorphic Function Type Mismatch
When trying to run a polymorphic function that abstracts over the type of the array, I get a type mismatch with the following error message:
Type mismatch: expected: (Int) => Boolean, actual: Int
...
- 92
7
votes
5
answers
7k
views
Writing a factorial tail recursive function in Scala
I'm trying to write a tail recursive function in the below way, but the compiler is throwing an error:
Too many arguments for method apply: (v1: Int)Int in trait Function1
else factorial(x-1, ...
- 93
1
vote
2
answers
875
views
Tail-recursive Implementation of Scala's List partition method
For exercise purposes I've been trying to implement a couple of Scala's List methods in a functional manner, one of them being partition. Assume the following signature:
def partition[T](l: List[T], ...
- 159
5
votes
4
answers
345
views
Rewriting imperative for loop to declarative style in Scala
How do I rewrite the following loop (pattern) into Scala, either using built-in higher order functions or tail recursion?
This the example of an iteration pattern where you do a computation (...
- 5,709
3
votes
1
answer
277
views
Why nested FlatMaps could blow up the stack in Scala?
I am learning the Trampoline trick in Scala by reading this paper Stackless Scala with Free Monad, by Rúnar Bjarnason. But I got stuck in section 4.3 "An easy thing to get wrong".
One thing makes me ...
- 51