自己写的练习题(yaht exercise 3.10)

izhier

只看了头三章
花了好长时间才写的这段代码
贴出来大家批评

1. 
   
2. yaht exercise 3.10:
   
3. Write a program that will repeatedly ask the user for numbers until she
   
4. types in zero, at which point it will tell her the sum of all the numbers, the product of
   
5. all the numbers, and, for each number, its factorial. For instance, a session might look
   
6. like:
   
7. Give me a number (or 0 to stop):
   
8. 5
   
9. Give me a number (or 0 to stop):
   
10. 8
    
11. Give me a number (or 0 to stop):
    
12. 2
    
13. Give me a number (or 0 to stop):
    
14. 0
    
15. The sum is 15
    
16. The product is 80
    
17. 5 factorial is 120
    
18. 8 factorial is 40320
    
19. 2 factorial is 2
    

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module Main where import IO factorial  0 = 1 factorial  n = n * factorial (n - 1) toNum s = read s + 0 toLine s =  s ++ " factorial is " ++ show (factorial (read s)) getList = do         putStrLn "Give me a number (or 0 to stop):"         word <- getLine         if word == "0"                 then return []                 else do                         rest <- getList                         return (word : rest) showFacLines (f:r) = do         if r == []                 then do                         putStrLn f                 else do                         putStrLn f                         showFacLines r main = do         list <- getList         if list == []                 then do                         putStrLn "You enter nothing!"                 else do                         putStrLn ("The sum is " ++ show (foldl (+) 0 (map toNum list)))                         putStrLn ("The product is " ++ show (foldl (*) 1 (map toNum list)))                         showFacLines (map toLine list)

izhier

vim 中设置　tab 是占四格的
没想到论坛中把　tab 转换成八个格了

izhier

缩进小了，果然好看 !

izhier

楼上代码很是漂亮

我要继续努力呀

izhier

倒是和　C 的代码布局有点神似
感觉这样挺好的

[ 本帖最后由 izhier 于 2009-3-25 20:45 编辑 ]

izhier

看来
haskell 的代码布局有点讲究
另开一帖，讲述一下，讨论讨论吧
愿闻其详

izhier

原来 yaht 后有答案！
贴出来答案的代码：

1. 
   
2. module Main
   
3.     where
   
4. 
   
5. import IO
   
6. 
   
7. main = do
   
8.   nums <- getNums
   
9.   putStrLn ("The sum is " ++ show (sum nums))
   
10.   putStrLn ("The product is " ++ show (product nums))
    
11.   showFactorials nums
    
12. 
    
13. getNums = do
    
14.   putStrLn "Give me a number (or 0 to stop):"
    
15.   num <- getLine
    
16.   if read num == 0
    
17.     then return []
    
18.     else do rest <- getNums
    
19.             return ((read num :: Int):rest)
    
20. 
    
21. showFactorials [] = return ()
    
22. showFactorials (x:xs) = do
    
23.   putStrLn (show x ++ " factorial is " ++
    
24.             show (factorial x))
    
25.   showFactorials xs
    
26. 
    
27. factorial 1 = 1
    
28. factorial n = n * factorial (n-1)
    

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izhier

只是觉得答案的代码写的比较好

izhier

原帖由 flw 于 2009-4-9 15:20 发表

好是相对的吧！
相对当时只看到那一节的人来说，也许确实不错。

:wink: