Запись списочных структур в точечной нотации

*Main> fun1 1 2 3
[1,2,3]
*Main> fun2 'a' 'b' "cd"
["ab","cd"]
*Main> fun4 4
[4]
*Main> fun5 [5,6] 7 8
[[5,6],[7,8]]
*Main> fun6
[[]]
*Main>

fun3::  [a] -> [a] -> a -> a -> [[a]]
fun3 a b c d = a:b:[c:[d]]

*Main> fun3 "Hellow" " worl" 'd' '!'
["Hellow"," worl","d!"]

main :: IO () 
main = do
  print $ fun1 1 2 3
  print $ fun2 'a' 'b' "cd"
  print $ fun3 "Hellow" " worl" 'd' '!'

fun6:: [[a]]
fun6 = [[]]
 
main :: IO () 
main = do
  print $ fun1 1 2 3
  print $ fun2 'a' 'b' "cd"
  print $ fun3 "Hellow" " worl" 'd' '!'
  print $ fun4 4
  print $ fun5 [5,6] 7 8
  print $ fun6 
 
-- Возвращает: main.hs:28:3: error:
--    • Ambiguous type variable ‘a0’ arising from a use of ‘print’
--      prevents the constraint ‘(Show a0)’ from being solved.
--      Probable fix: use a type annotation to specify what ‘a0’ should be.
--      These potential instances exist:
--        instance Show Ordering -- Defined in ‘GHC.Show’
--        instance Show Integer -- Defined in ‘GHC.Show’
--        instance Show a => Show (Maybe a) -- Defined in ‘GHC.Show’
--        ...plus 22 others
--        ...plus 11 instances involving out-of-scope types
--        (use -fprint-potential-instances to see them all)
--    • In a stmt of a 'do' block: print $ fun6
--      In the expression:
--        do print $ fun1 1 2 3
--           print $ fun2 'a' 'b' "cd"
--           print $ fun3 "Hellow" " worl" 'd' '!'
--           print $ fun4 4
--           ....
--      In an equation for ‘main’:
--         main
--            = do print $ fun1 1 2 3
--                 print $ fun2 'a' 'b' "cd"
--                 print $ fun3 "Hellow" " worl" 'd' '!'
--                 ....
--   |
--28 |   print $ fun6
--   |   ^^^^^^^^^^^^

fun6 :: [[Int]]
fun6 = [[]]
 
main :: IO () 
main = do
  print $ fun6

  print (fun6 :: [[Int]])

fn:: a->a->[a]
fn a b =a:b:[]
 
fun::a->[a]
fun a =[a]
 
 
main=do 
print(fn 1 2)
print(fn [1] [2])
print (fn[1,2][3,4,5])
print(fn [10](fn 11 12))
 
print (fun 20)
print(fun [33])
print(fun[fn[13](fn 14 25)])