{-# OPTIONS_GHC -dsuppress-all -dno-suppress-type-signatures -dno-typeable-binds -dsuppress-uniques #-}
module Prec where
 
import Data.Foldable
import Data.Maybe

data Value = A | B | C | D | E
  deriving Eq

prec' :: Value -> [[Value]] -> Int
prec' v = fromMaybe 0 . foldl' f Nothing
  where
    f (Just !len) _ = Just (len + 1)
    f Nothing vs | v `elem` vs = Just 1
                 | otherwise = Nothing
{-# INLINE prec' #-}

order :: [[Value]]
order = [
  [ B ],
  [ A, D ],
  [ C ]
  ]
{-# INLINE order #-}
  
prec :: Value -> Int
prec v = prec' v order