Solution 1 for Project Euler problem 1 written in Elm

App.elm

-- we will show the result with a single html text node
import Html exposing (text)

-- let's call the function euler1 and say it receives a single Int param and returns a single Int param
euler1 : Int -> Int
euler1 num =
  -- break point of the recursion is when num is 0
  if num == 0 then
    0
  else
    -- check if the number is divisable by 3 or 5
    if num % 3 == 0 || num % 5 == 0 then
      -- if yes, return the sum of the number and any other numbers detected
      num + euler1 (num-1)
    else
      -- if no, skip this number, go look for others and return their sum
      euler1 (num-1)
    
    
main =
  -- convert from String to Int and show the result with a text node
  -- 10-1 because we need to find all numbers below 10
  text ( toString ( euler1 (10-1) ) )