$ ghci 01_intro_inter.hs
GHCi, version 7.0.4: http://www.haskell.org/ghc/  :? for help
Loading package ghc-prim ... linking ... done.
Loading package integer-gmp ... linking ... done.
Loading package base ... linking ... done.
[1 of 1] Compiling Main             ( 01_intro_inter.hs, interpreted )
Ok, modules loaded: Main.
*Main> let x = ((1,2),(3,4))
*Main> fst x
(1,2)
*Main> fst fst x

<interactive>:1:5:
    Couldn't match expected type `(t1 -> t0, b0)'
                with actual type `(a0, b1) -> a0'
    In the first argument of `fst', namely `fst'
    In the expression: fst fst x
    In an equation for `it': it = fst fst x
*Main> fst (fst x)
1
*Main> fst $ fst x
1
*Main> let x = ... in nth x (1,2,3)
*Main> 1:2:5

<interactive>:1:5:
    No instance for (Num [a0])
      arising from the literal `5'
    Possible fix: add an instance declaration for (Num [a0])
    In the second argument of `(:)', namely `5'
    In the second argument of `(:)', namely `2 : 5'
    In the expression: 1 : 2 : 5
*Main> :info String
type String = [Char]    -- Defined in GHC.Base
*Main> :type "Hello"
"Hello" :: [Char]
*Main> :load 01_intro_inter.hs 
[1 of 1] Compiling Main             ( 01_intro_inter.hs, interpreted )
Ok, modules loaded: Main.
*Main> let mypair = (1,2)
*Main> case mypair of (a,b) | a == 1 -> (a,b)
(1,2)
*Main> case (2,3) of (a,b) | a == 1 -> (a,b)
*** Exception: <interactive>:1:1-37: Non-exhaustive patterns in case

*Main> map (\x y -> x + (2*y)) [1,2,3]

<interactive>:1:1:
    No instance for (Show (a0 -> a0))
      arising from a use of `print'
    Possible fix: add an instance declaration for (Show (a0 -> a0
))
    In a stmt of an interactive GHCi command: print it
*Main> :type map (\x y -> x + (2*y)) [1,2,3]
map (\x y -> x + (2*y)) [1,2,3] :: Num a => [a -> a]
*Main> map (\f -> f 7) $ map (\x y -> x + (2*y)) [1,2,3]
[15,16,17]