List members of union in PureScript

Main.purs

module Main where

import Prelude
import Data.Enum
import Data.Maybe
import Data.List

import Effect
import TryPureScript 

data Size = Small | Medium | Large

instance showSize :: Show Size where
  show Small = "small"
  show Medium = "medium"
  show Large = "large"

derive instance eqSize :: Eq Size
derive instance ordSize :: Ord Size

instance enumSize :: Enum Size where
  succ Small = Just Medium
  succ Medium = Just Large
  succ Large = Nothing
  pred Small = Nothing
  pred Medium = Just Small
  pred Large = Just Medium
  
instance boundedSize :: Bounded Size where
  bottom = Small
  top = Large

main :: Effect Unit
main =
    render $ list (map textSize sizes)
  where
    sizes :: List Size
    sizes = enumFromTo bottom top
    
    textSize size = text (show size)