因为是刚开始看
haskell
所以很多概念不是很清楚，比如何时用
do
、“
<-
”和
let
。
Exerceise3.10
算是做出来，但是肯定不是一个好办法。希望给我改改吧，顺便解答一下我的疑问。不得不说的是编译信息相当地没有用啊，这真是太遗憾了。
module
Main
where
import IO
main = do
list <- askForNumber
let
sAdd = show (foldl (+) 0 list)
sMul = show (foldl (*) 1 list)
putStrLn ("The sum is " ++ sAdd)
putStrLn ("The production is " ++
sMul)
putFactorial list
askForNumber
= do
putStrLn "Give me a number (or 0 to
top):"
sNum <- getLine
let num = read sNum
if num == 0
then return []
else do
rest
<- askForNumber
return (num : rest)
putFactorial
[] = do
putStr ""
putFactorial
(x : rest) = do
let fact = factorial x
putStrLn ((show x) ++ " factorial is
" ++ (show fact))
putFactorial(rest)
factorial
1 = 1
factorial
x = x * factorial (x-1)