Ok, one module loaded.
*Main> nodes tr1
4
*Main> :r
[1 of 1] Compiling Main             ( lec5.hs, interpreted )
Ok, one module loaded.
*Main> height tr1
3
*Main> :r
[1 of 1] Compiling Main             ( lec5.hs, interpreted )
Ok, one module loaded.
*Main> mapTree even tr1 
Node False (Node True Leaf Leaf) (Node True (Node False Leaf Leaf) Leaf)
*Main> mapTree (\ x -> x + 1) tr1 
Node 6 (Node 5 Leaf Leaf) (Node 7 (Node 8 Leaf Leaf) Leaf)
*Main> :r
[1 of 1] Compiling Main             ( lec5.hs, interpreted )
Ok, one module loaded.
*Main> :r
[1 of 1] Compiling Main             ( lec5.hs, interpreted )
Ok, one module loaded.
*Main> nodes' tr1
4
*Main> :r
[1 of 1] Compiling Main             ( lec5.hs, interpreted )
Ok, one module loaded.
*Main> height' tr1
3
*Main> :r
[1 of 1] Compiling Main             ( lec5.hs, interpreted )
Ok, one module loaded.
*Main> depthFirst tr2
[5,9,6,8,7]
*Main> :r
[1 of 1] Compiling Main             ( lec5.hs, interpreted )
Ok, one module loaded.
*Main> :r
[1 of 1] Compiling Main             ( lec5.hs, interpreted )
Ok, one module loaded.
*Main> breadthFirst tr2
[8,9,7,5,6]
*Main> breadthFirst tr1
[5,4,6,7]
*Main> :r
[1 of 1] Compiling Main             ( lec5.hs, interpreted )
Ok, one module loaded.
*Main> breadthFirst tr1
[5,4,6,7]
*Main> breadthFirst tr2
[8,9,7,5,6]
*Main> :t lookup
lookup :: Eq a => a -> [(a, b)] -> Maybe b
*Main> :r
[1 of 1] Compiling Main             ( lec5.hs, interpreted )
Ok, one module loaded.
*Main> my_lookup (zip [1..10] "a..z") 5
*** Exception: doesn't exist
CallStack (from HasCallStack):
  error, called at lec5.hs:62:18 in main:Main
*Main> "a .. z"
"a .. z"
*Main> ['a' .. 'z']
"abcdefghijklmnopqrstuvwxyz"
*Main> my_lookup (zip [1..10] ['a' .. 'z']) 5
'e'
*Main> my_lookup (zip [1..10] ['a' .. 'z']) 10
'j'
*Main> my_lookup (zip [1..10] ['a' .. 'z']) 11
*** Exception: doesn't exist
CallStack (from HasCallStack):
  error, called at lec5.hs:62:18 in main:Main
*Main> :r
[1 of 1] Compiling Main             ( lec5.hs, interpreted )
Ok, one module loaded.
*Main> my_lookup' (zip [1..10] ['a' .. 'z']) 10
Just 'j'
*Main> my_lookup' (zip [1..10] ['a' .. 'z']) 5
Just 'e'
*Main> my_lookup' (zip [1..10] ['a' .. 'z']) 11
Nothing