recursion - How to write a function finding even numbers in list on F#

Question

Hello guys so i have a problem about finding even numbers in the list. Im so new in F# and i need to find even numbers in the list with function.

I have the real question:

//Given is a list of integers. Write a recursive function that returns a pair of lists: a list of even numbers //and a list of numbers divisible by three. For example, for the list [1; 2; 3; 4; 5; 6] we should get ([2; 4; 6], [3; 6]).

I tried this :

let list1 = [1; 2; 3; 4; 5; 6; 7; 8; 9; 10]
let evens list1 =
   let isEven x = x % 2 = 0  
                              
   List.filter isEven list1  
                              

But its not working. Thank you for your help.

question from:https://stackoverflow.com/questions/65853528/how-to-write-a-function-finding-even-numbers-in-list-on-f

Answer 1

What you've got is correct for finding even numbers. The only thing missing is that you need to call your evens function, passing it list1, like this: evens list1.

Keep in mind that the parameters of a function are different from its arguments. In this case, you've called both the parameter and the argument list1, which may be confusing you.

Here's a complete version, using two different names for clarity:

let myList = [1; 2; 3; 4; 5; 6; 7; 8; 9; 10]
let evens anyList =
   let isEven x = x % 2 = 0  
   List.filter isEven anyList
printfn "%A" (evens myList)

Once you understand how this works, you can try solving the full problem you mentioned.