Practice N Queen problem in term level PureScript

Main.purs

module Main where

import Prelude

import Control.Monad.Eff (Eff)
import Control.Monad.Eff.Console (logShow, CONSOLE)
import Data.Ord (abs)
import Data.List (List(Nil), mapWithIndex, range, (:), filter, length, foldl)
import Data.Foldable (all)
import Data.Traversable (traverse)
import TryPureScript (render, withConsole, DOM)

checkVertical :: List Int -> Int -> Boolean
checkVertical arr n = all (_ /= n) arr

checkDiagonal :: List Int -> Int -> Boolean
checkDiagonal arr cc = all id $ mapWithIndex checkOne arr
  where
    checkOne r c = abs (r + 1 - 0) /= abs (c - cc)

-- check whether n can be prepend to the arr
check :: List Int -> Int -> Boolean
check arr n = checkDiagonal arr n && checkVertical arr n

-- place one by prepend
placeOne :: Int -> List Int -> List (List Int)
placeOne n arr =
  range 0 (n - 1)
    # filter (check arr)
    # map (_ : arr) 

nQueen :: Int -> List (List Int)
nQueen n = go Nil Nil
  where
    go acc arr
      | length arr == n = arr : acc
      | otherwise = foldl go acc $ placeOne n arr

main :: forall eff. Eff (dom :: DOM, console :: CONSOLE | eff) Unit
main = render =<< withConsole do
  range 1 10 #
    traverse (logShow <<< length <<< nQueen)