*Main> tree1
Node "f" (Node "e" (Leaf "c") (Leaf "d")) (Node "g" (Leaf "a") (Leaf "b"))
*Main> depth tree1

<interactive>:4:1: error:
    • No instance for (Show (State [[Char]] ()))
        arising from a use of ‘print’
    • In a stmt of an interactive GHCi command: print it
*Main> depth tree1

<interactive>:7:1: error:
    • No instance for (Show (State [[Char]] ()))
        arising from a use of ‘print’
    • In a stmt of an interactive GHCi command: print it
*Main> runState [] (depth tree1)
((),["c","e","d","f","a","g","b"])
*Main> runState [] (depth tree1)
((),["c","e","d","f","a","g","b"])
*Main> :t (>>)
(>>) :: Monad m => m a -> m b -> m b
*Main> :t (>>=)
(>>=) :: Monad m => m a -> (a -> m b) -> m b
*Main> breadth

<interactive>:17:1: error:
    • No instance for (Show (State [Tree a0] [a0]))
        arising from a use of ‘print’
    • In a stmt of an interactive GHCi command: print it
*Main> runState [tree1] breadth 
(["f","e","g","c","d","a","b"],[])
*Main> tree1
Node "f" (Node "e" (Leaf "c") (Leaf "d")) (Node "g" (Leaf "a") (Leaf "b"))
*Main> :t getChar
getChar :: IO Char
*Main> getChar
a
'a'
*Main> *Main> putChar 'c'
c*Main> :r
*Main> sequenceIO [putChar 'a', putChar 'b', putChar 'c', putChar '\n']
abc
*Main> putString "hello"
hello*Main> putString "hello\n"
hello
*Main> putString' "hello\n"
hello
*Main> echo
m
m
p
p
a
aa*Main> *Main>