Question

I’ve written following code:

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"

And in no.txt:

one
two
three
four
....

After compiled and run the code, I got the result:

1

But I expect to get:

1
2
3
4
...

What’s wrong with the code? Any help? thx!

Answer 1

str is not list of String (it’s just a String like one\ntwo) when read from readFile. Do

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

in your main instead and convert str to a list using lines (see doc of lines ).