File Haskell文件读取和添加数字

我有一个程序，它采用一个带有值的文本文件，例如：

20 30
23 5
200 3

我把它转换成一个列表，把每一行加起来，创建一个小计，然后是一个总和

import System.IO  
import Control.Monad

f :: [String] -> [Int]
f = map read

subsum :: [Int] -> [Int]
subsum [] = []
subsum [x] = []
subsum (x:(y:xs)) = (x+y) : (subsum xs)

calc fromf = do  
        let list = []  
        let list2 = []
        handle <- openFile fromf ReadMode
        contents <- hGetContents handle
        let singlewords = words contents
            list = f singlewords
            list2 = subsum list
            result = sum list2
        print list2
        print result
        hClose handle  

创建每行小计的列表，然后创建总计。

如何

import System.IO
import Control.Monad

subtotals :: String -> [Int]
subtotals c = map sum (map (map readInt) (map words (lines c)))
    where
        readInt = read :: String -> Int

calc fname = do
    contents <- readFile fname
    print $ subtotals contents
    print $ sum (subtotals contents)

import System.IO
进口管制
小计：：字符串->[Int]
小计c=映射和（映射（映射读取）（映射字（行c）））
哪里
readInt=read:：String->Int
calc fname=do
内容您的
list=[]
和
list2=[]
语句是不必要的。这些是不可变的变量（与其他语言一样），因此您可能无法完成初始化之类的操作。readInt在我的股票GHC 7.10.2中未定义。我用自己的函数“readInt:：[String]->[Int]；readInt=map read”替换了它
import System.IO
import Control.Monad

subtotals :: String -> [Int]
subtotals c = map sum (map (map readInt) (map words (lines c)))
    where
        readInt = read :: String -> Int

calc fname = do
    contents <- readFile fname
    print $ subtotals contents
    print $ sum (subtotals contents)