Haskell显示字符串分为8列 [英] Haskell Display String into 8 columns

问题描述

我有类型人员=(字符串，浮点数，浮点数，[Int])**名称，身高，体重，过去一周的英里数**

I have type person = (String, Float, Float, [Int]) ** name, height, weight, miles walked past week**

[Int]将包含该人在过去7天内每天走了多少英里的数据例如[5,8,12,7,12,6,9]

The [Int] will contain data for how many miles the person walked on each day for the past 7 days e.g. [5,8,12,7,12,6,9]

我的testData由多个人数据组成，我想以一个字符串的形式返回他们走过的里程的所有名称和7个每日数字，整齐地分成每个人的单独行，并将走过的里程数据按列排列.

My testData consists of multiple peoples data and I want to return all names and the 7 daily figures of the miles they walked as a single string, neatly into separate rows for each person and have the miles walked data lined up in columns.

例如testData = [(John，1.76，63，[5,8,12,7,12,6,9])，(Hannah，1.64，56，[6,9,10,9,5,13,​​13])，(刘易斯，1.80、73，[4,6,2,6,8,4,6])]

e.g. testData = [(John, 1.76, 63, [5,8,12,7,12,6,9]), (Hannah, 1.64, 56, [6,9,10,9,5,13,13]), (Lewis, 1.80, 73, [4,6,2,6,8,4,6])]

我希望这样返回:

返回结果

在haskell中执行此操作的最佳方法是什么?谢谢

what is the best way to do this in haskell? Thanks

我的代码-

personToString :: [Person] -> String   
personToString [] = []   
personToString ((name,height,weight,miles):person)=   
   name ++ take (9 - length name) (cycle " ") ++ intercalate ", " (map show miles) ++ "\n \n" ++ personToString person  

这将返回我想要的内容，但英里数未对齐，因为有一位数字和两位数字的组合

This returns what I want but the miles digits don't line up as there is a mix of single and double digit figures

推荐答案

好的，有人麻烦将模块

OK, somebody took the trouble of putting together module Text.Printf.

这里似乎只是裁员了，所以让我们尝试一下:

Seems just a job cut for it here, so let's give it a try:

import  Data.List (intercalate)
import  Text.Printf

type Person = (String, Float, Float, [Int]) -- ** name, height, weight, miles...

testData  :: [Person]
testData = [("John",   1.76, 63, [5,8,12,7,12,6,9]),
            ("Hannah", 1.64, 56, [6,9,10,9,5,13,13]),
            ("Lewis",  1.80, 73, [4,6,2,6,8,4,6])]

showMileList :: [Int] -> String
showMileList mileList = intercalate ","  $
                            map (printf "%3d") mileList

personToString :: Person -> String
personToString (name, h, w, miles) =
    (printf "%-9s" name) ++ " "                    ++
       (printf "%5.2f " h) ++ (printf "%3.0f " w)  ++
       (showMileList miles)

printAsLines :: [String] -> IO ()
printAsLines xs = mapM_ putStrLn  xs  -- a loop in the IO monad


main = do
   let strings = map  personToString  testData
   printAsLines strings

程序输出:

John       1.76  63   5,  8, 12,  7, 12,  6,  9
Hannah     1.64  56   6,  9, 10,  9,  5, 13, 13
Lewis      1.80  73   4,  6,  2,  6,  8,  4,  6

我发现这很容易，在ghci下很难使用该模块: printf 上键入内容的任何松动似乎都会破坏交互式编译器.

Sole hitch in the deal I could find, the module is a bit hard to use under ghci: any looseness in the typing around printf seems to derail the interactive compiler.

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