Step by Step solution about How to resolve the algorithm Text processing/1 step by step in the Haskell programming language

This Haskell program reads data from a file, parses it into a list of tuples containing a date and a list of values and flags, and then processes the data to find summary statistics and maximum runs of consecutive false readings.

Here's a detailed explanation of the code:

1. Importing Modules: The program imports several Haskell modules for various functionalities:

   • Data.List: For list manipulation functions.
   • Numeric: For numeric data handling.
   • Control.Arrow: For function composition.
   • Control.Monad: For monad operations.
   • Text.Printf: For formatted printing.
   • System.Environment: For accessing command-line arguments.
   • Data.Function: For function utilities.

2. Type Declarations:

   • Date: The type representing a date, defined as a string.
   • Value: The type representing a value, defined as a double-precision floating-point number.
   • Flag: The type representing a flag, defined as a boolean.

3. Auxiliary Functions:

   • readFlg: Converts a string to a boolean flag, returning True if the numeric value of the string is greater than 0, and False otherwise.
   • readNum: Converts a string to a numeric value.
   • take2: Takes a list of strings and splits it into pairs, using an unfoldr function.

4. parseData Function: Parses a list of strings into a tuple containing a date and a list of value-flag pairs. The date is the first string in the list, and the value-flag pairs are extracted from the remaining strings using the take2 function.

5. sumAccs Function: Processes a tuple representing a date and a list of value-flag pairs. It sums the values for each flag, counts the number of values for each flag, and combines the results into a tuple containing the date, a list of tuples representing the average and count of values for each flag, and a list of flags.

6. maxNAseq Function: Finds the maximum run of consecutive false readings in a list of flags. It does this by grouping the flags by consecutive false readings, sorting the groups by length, and then returning the maximum group.

7. main Function:

   • Reads the command-line arguments and extracts the file name.
   • Reads the file and splits each line into a list of strings.
   • Parses the data using the parseData function.
   • Processes the data using the sumAccs function to compute summary statistics.
   • Finds the maximum run of consecutive false readings using the maxNAseq function.
   • Prints the summary statistics and the maximum run of consecutive false readings.

The program takes a file as input, where each line represents a data record containing a date, a value, and a flag. It parses the data, calculates summary statistics, and identifies the maximum run of consecutive false readings. Finally, it prints the results.

import Data.List
import Numeric
import Control.Arrow
import Control.Monad
import Text.Printf
import System.Environment
import Data.Function

type Date = String
type Value = Double
type Flag = Bool

readFlg :: String -> Flag
readFlg = (> 0).read

readNum :: String -> Value
readNum = fst.head.readFloat

take2 = takeWhile(not.null).unfoldr (Just.splitAt 2)

parseData :: [String] -> (Date,[(Value,Flag)])
parseData = head &&& map(readNum.head &&& readFlg.last).take2.tail

sumAccs :: (Date,[(Value,Flag)]) -> (Date, ((Value,Int),[Flag]))
sumAccs = second (((sum &&& length).concat.uncurry(zipWith(\v f -> [v|f])) &&& snd).unzip)

maxNAseq :: [Flag] -> [(Int,Int)]
maxNAseq = head.groupBy((==) `on` fst).sortBy(flip compare)
           . concat.uncurry(zipWith(\i (r,b)->[(r,i)|not b]))
           . first(init.scanl(+)0). unzip
           . map ((fst &&& id).(length &&& head)). group

main = do
    file:_ <- getArgs
    f <- readFile file
    let dat :: [(Date,((Value,Int),[Flag]))]
        dat      = map (sumAccs. parseData. words).lines $ f
        summ     = ((sum *** sum). unzip *** maxNAseq.concat). unzip $ map snd dat
        totalFmt = "\nSummary\t\t accept: %d\t total: %.3f \taverage: %6.3f\n\n"
        lineFmt  = "%8s\t accept: %2d\t total: %11.3f \taverage: %6.3f\n"
        maxFmt   =  "Maximum of %d consecutive false readings, starting on line /%s/ and ending on line /%s/\n"
-- output statistics
    putStrLn "\nSome lines:\n"
    mapM_ (\(d,((v,n),_)) -> printf lineFmt d n v (v/fromIntegral n)) $ take 4 $ drop 2200 dat 
    (\(t,n) -> printf totalFmt  n t (t/fromIntegral n)) $ fst summ
    mapM_ ((\(l, d1,d2) -> printf maxFmt l d1 d2)
              . (\(a,b)-> (a,(fst.(dat!!).(`div`24))b,(fst.(dat!!).(`div`24))(a+b)))) $ snd summ


*Main> :main ["./RC/readings.txt"]