https://www.codewars.com/kata/514b92a657cdc65150000006

multipleOf3And5.hs

module MultiplesOf3And5 where

solution :: Integer -> Integer
solution number = solutionInner (number - 1) 0

solutionInner :: Integer -> Integer -> Integer
solutionInner number total =
  if   number <= 0
  then total
  else solutionInner number' total'
  where
    number' = number - 1
    total'  =
      if   number `divisibleBy` 3 || number `divisibleBy` 5
      then total + number
      else total
      
divisibleBy :: Integer -> Integer -> Bool
divisibleBy n d = mod' == 0
  where
    mod' = n `mod` d