truth_tables.hs

import Data.List
import Control.Applicative

main :: IO ()
main = do
    let tt = [True, True]
        ff = [False, False]
        tf = head perms_tf
        ft = reverse (head perms_tf)
        perms_tf = permutations [True, False]
        perms_tbl = tt:tf:ft:[ff]
    putStrLn "Negation"
    putStrLn $ show([True, not True])
    putStrLn "Conjunction"
    fmap putStrLn show(map and perms_tbl)
    putStrLn "Disjunction"
    fmap putStrLn show(map or perms_tbl)
    putStrLn "Implication"
    fmap putStrLn show ([(<=) x (head y) | (x:y) <- perms_tbl])
    putStrLn "Equivalence"
    -- thanks to ion on IRC, who answered my query with
    -- (P -> Q, Q -> P)?
    fmap putStrLn show ([((<=) x (head y)) && ((<=) (head y) x) | (x:y) <- perms_tbl])
    return ()