Real World Haskell - 第1章 練習問題
Real World Haskell を継続的に勉強中。
Exercises
1. Enter the following expressions into ghci. What are their types?
* 5 + 8
* 3 * 5 + 8
* 2 + 4
* (+) 2 4
* sqrt 16
* succ 6
* succ 7
* pred 9
* pred 8
* sin (pi / 2)
* truncate pi
* round 3.5
* round 3.4
* floor 3.7
* ceiling 3.32. From ghci, type :? to print some help. Define a variable, such as let x = 1, then type :show bindings. What do you see?
3. The words function counts the number of words in a string. Modify the WC.hs example to count the number of words in a file.
4. Modify the WC.hs example again, to print the number of characters in a file.
1
Prelude> :set +t Prelude> 5+8 13 it :: Integer Prelude> 3*5+8 23 it :: Integer Prelude> 2+4 6 it :: Integer Prelude> (+) 2 4 6 it :: Integer Prelude> sqrt 16 4.0 it :: Double Prelude> succ 6 7 it :: Integer Prelude> succ 7 8 it :: Integer Prelude> pred 9 8 it :: Integer Prelude> pred 8 7 it :: Integer Prelude> sin (pi/2) 1.0 it :: Double Prelude> truncate pi 3 it :: Integer Prelude> round 3.5 4 it :: Integer Prelude> round 3.4 3 it :: Integer Prelude> floor 3.7 3 it :: Integer Prelude> ceiling 3.3 4 it :: Integer Prelude>
2
Prelude> let x = 1 Prelude> :show bindings x :: Integer = _ Prelude>
3
main = interact wordCount where wordCount input = show (length (words input)) ++ "\n"
4
main = interact wordCount where wordCount input = show (length input) ++ "\n"
参考