Question

我有一个程序，它带有一个带有值的文本文件，例如：

20 30
23 5
200 3

我将其转换为列表并添加每一行以创建小计，然后是总和。

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

如何更改此代码以获取不同数字的文本文件ex：

10 9 29 40
1 34 2
1 2 55 89

创建每行的小计列表，然后创建总计。

Answer 1

怎么样

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)

Haskell文件读取和添加数字

1 个答案: