map join a traverse - illustration for a reddit question https://www.reddit.com/r/purescript/comments/aq31gu/i_feel_like_this_is_probably_a_standard_function/

Main.purs

module Main where

import Prelude

import Data.Array (range) as Array
import Data.Traversable (traverse)
import Effect.Aff (Aff)


combineABunchOfArrays :: Aff (Array Int)
combineABunchOfArrays = 
  traverse makeArray (Array.range 0 10) # map join

combineABunchOfArrays2 :: Aff (Array Int)
combineABunchOfArrays2 = 
  join <$> traverse makeArray (Array.range 0 10)


makeArray :: Int -> Aff (Array Int)
makeArray num = pure $ Array.range 0 num