A Collection of Code Snippets in as Many Programming Languages as Possible

This project is maintained by TheRenegadeCoder

Welcome to the Merge Sort in Haskell page! Here, you'll find the source code for this program as well as a description of how the program works.

```
module Main where
import Text.Read
import System.Environment
import System.Exit (exitWith, ExitCode(ExitFailure))
import Data.List (intercalate)
mergeSort :: Ord a => [a] -> [a]
mergeSort xs = head $ mergeSort' $ fmap (:[]) xs
where mergeSort' :: Ord a => [[a]] -> [[a]]
mergeSort' [] = []
mergeSort' [x] = [x]
mergeSort' (x1:x2:xs) = mergeSort' $ merge x1 x2:mergeSort' xs
merge :: Ord a => [a] -> [a] -> [a]
merge x [] = x
merge [] y = y
merge (x:xs) (y:ys)
| x < y = x:merge xs (y:ys)
| otherwise = y:merge (x:xs) ys
headMaybe :: [a] -> Maybe a
headMaybe [] = Nothing
headMaybe (x:xs) = Just x
-- Converts string in format "1, 2, 3" to a Maybe list of int
stringToListMaybe :: String -> Maybe [Int]
stringToListMaybe str = readMaybe $ "[" ++ str ++ "]" :: Maybe [Int]
-- Ensure that a list contains at least two elements
verifyListLength :: Ord a => [a] -> Maybe [a]
verifyListLength [] = Nothing
verifyListLength [x] = Nothing
verifyListLength (x:xs) = Just (x:xs)
listToString :: [Int] -> String
listToString = intercalate ", " . map show
main :: IO ()
main = do
args <- getArgs
let xs = headMaybe args >>= stringToListMaybe >>= verifyListLength
case xs of
Nothing -> do
putStrLn "Usage: please provide a list of at least two integers to sort in the format \"1, 2, 3, 4, 5\""
exitWith $ ExitFailure 1
Just xs -> putStrLn $ listToString $ mergeSort xs
```

Merge Sort in Haskell was written by:

- Parker Johansen

If you see anything you'd like to change or update, please consider contributing.

No 'How to Implement the Solution' section available. Please consider contributing.

No 'How to Run the Solution' section available. Please consider contributing.