Haskell - 打印数字

Question

我写了下面的代码:

module Test where

import Char
import IO

main = do
    str <- readFile "no.txt"
    putStrLn (show(english str))

string2list :: String -> [String]
string2list "" = []
string2list s = words s


english :: String -> Int
english s
    | head (string2list s) == "one"     = 1
    | head (string2list s) == "two"     = 2
    | head (string2list s) == "three"   = 3
    | head (string2list s) == "four"    = 4
    | head (string2list s) == "five"    = 5
    | head (string2list s) == "six"     = 6
    | head (string2list s) == "seven"   = 7
    | head (string2list s) == "eight"   = 8
    | head (string2list s) == "nine"    = 9
    | otherwise                         = error "not match"

在 no.txt 中:

one
two
three
four
....

编译运行代码后，得到结果:

1

但我希望得到:

1
2
3
4
...

代码有什么问题？有什么帮助吗？谢谢!

Answer 1

从 readFile 读取时，

str 不是字符串列表(它只是一个类似于 one\ntwo 的字符串)。做

main = do
    str <- readFile "no.txt"
    mapM_ (\x -> putStrLn (show(english x))) $ lines str

在您的 main 中使用 lines 将 str 转换为列表(参见 lines 的文档)。