Here are my answers to the exercises of chapter 1.

1. Enter the following expressions into ghci What are their types?

Prelude> 5 + 8
5 + 8
13
it :: Integer
Prelude> 3 * 5 + 8
3 * 5 + 8
23
it :: Integer
Prelude> 2 + 4
2 + 4
6
it :: Integer
Prelude> (+) 2 4
(+) 2 4
6
it :: Integer
Prelude> sqrt 16
sqrt 16
4.0
it :: Double
Prelude> succ 6
succ 6
7
it :: Integer
Prelude> succ 7
succ 7
8
it :: Integer
Prelude> pred 9
pred 9
8
it :: Integer
Prelude> pred 8
pred 8
7
it :: Integer
Prelude> sin (pi / 2)
sin (pi / 2)
1.0
it :: Double
Prelude> truncate pi
truncate pi
3
it :: Integer
Prelude> round 3.5
round 3.5
4
it :: Integer
Prelude> round 3.4
round 3.4
3
it :: Integer
Prelude> floor 3.7
floor 3.7
3
it :: Integer
Prelude> ceiling 3.3
ceiling 3.3
4
it :: Integer

2. From ghci, type :? to print some help. Define a variable and then type :show bindings. What do you see?

Prelude> let x = 1
let x = 1
Prelude> :show bindings
:show bindings
it :: Integer = 4
x :: Integer = _
Prelude> x
x
1
Prelude> :show bindings
:show bindings
it :: Integer = 4
x :: Integer = 1

3. The words function counts the number of words in a string. Modify the WC.hs example in order to count the number of words in a file.

main = interact wordCount
  where wordCount input = show (length (words input)) ++ "n"

4. Modify the WC.hs example again, in order to print the number of characters in a file.

main = interact wordCount
  where wordCount input = show (length input) ++ "n"