A small script to determine your final grade :)

determineFinalGrade.hs

{-# LANGUAGE LambdaCase #-}

import Data.List (sort)
import Control.Monad (unless)

data Grade = Grade {
    grade :: Float,
    credits :: Int
}

instance Show Grade where
    show (Grade g c) = show g ++ " (" ++ show c ++ "CP)"

getBestGradesWithNCPs :: Int -> [Grade] -> [Float]
getBestGradesWithNCPs n = take n . sort . concatMap normalize

normalize :: Grade -> [Float]
normalize (Grade g c) = replicate c g

readGrade :: IO (Maybe Grade)
readGrade = parseGrade <$> getLine

parseGrade :: String -> Maybe Grade
parseGrade s = case words s of
    [g, c] -> Just $ Grade (read g) (read c)
    _ -> Nothing

readGrades :: IO [Grade]
readGrades = do
    line <- getLine
    case parseGrade line of
        Just grade -> (:) grade <$> readGrades
        Nothing -> return []

changeNth :: Int -> a -> [a] -> [a]
changeNth n x xs = take n xs ++ (x : drop (n + 1) xs)

removeNth :: Int -> [a] -> [a]
removeNth _ [] = []
removeNth 0 (_:xs) = xs
removeNth i (x:xs) = x:removeNth (i-1) xs

calc :: [Grade] -> Float
calc grades = do
    let ma = filter ((==30) . credits) grades
    let bestGrades = getBestGradesWithNCPs 74 grades
    if length ma == 1 then do
        let normalizedMa = normalize $ head ma
        sum (bestGrades ++ normalizedMa) / fromIntegral (length bestGrades + length normalizedMa)
    else sum bestGrades / fromIntegral (length bestGrades)


loop grades = do
    print "What do you want to do? r: print result, q: quit, i: insert grade, d: delete grade, c: change grade, l: list grades"
    mode :: Char <- getChar
    putStrLn ""
    case mode of
        'q' -> return ()
        'l' -> print grades >> loop grades
        'r' -> print (calc grades) >> loop grades
        'i' -> do
            print "Enter the grade in the format 'grade credits' (e.g. '1.0 6'):"
            readGrade >>= \case
                Just grade -> loop $ grades ++ [grade]
                Nothing -> print "Invalid input" >> loop grades
        'd' -> do
            print "Enter the index you want to delete:"
            i :: Int <- read <$> getLine
            loop $ removeNth i grades
        'c' -> do
            print "Enter the index you want to change:"
            i :: Int <- read <$> getLine
            print "Enter the new grade in the format 'grade credits' (e.g. '1.0 6'):"
            readGrade >>= \case
                Just grade -> loop $ changeNth i grade grades
                Nothing -> print "Invalid input" >> loop grades

main = do
    print "Enter your grades line by line in the format 'grade credits' (e.g. '1.0 6'):"
    grades <- readGrades
    print "Thanks!"
    loop grades