command-line.txt

$ ghc -O3 fold_elem.hs
$ time ./fold_elem foldr
True
./fold_elem foldr  1.59s user 0.01s system 99% cpu 1.602 total
$ time ./fold_elem foldl
True
./fold_elem foldl  2.96s user 0.01s system 99% cpu 2.978 total
$ time ./fold_elem rec  
True
./fold_elem rec  1.63s user 0.00s system 99% cpu 1.638 total

elem_fold.hs

module Main
  where

import System.Environment

elem_foldr:: (Eq a, Foldable t) => a -> t a -> Bool
elem_foldr x = foldr (\y acc -> x == y || acc) False

elem_foldl:: (Eq a, Foldable t) => a -> t a -> Bool
elem_foldl x = foldl (\acc y -> acc || x == y) False

elem_rec:: Eq a => a -> [a] -> Bool
elem_rec _ [] = False
elem_rec x (y:ys) = x == y || elem_rec x ys


main:: IO ()
main = do
  -- let e = 100000000::Integer
  -- let e = 1::Integer
  let e = 200000000::Integer
  let list = [1..200000000]
  args <- getArgs
  case head args of
    "foldr" -> putStrLn $ show $ elem_foldr e list
    "foldl" -> putStrLn $ show $ elem_foldl e list
    "rec" -> putStrLn $ show $ elem_rec e list
    _ -> return ()