AnkiMath.hs

module Main (makeCards, main) where

import Data.List
import System.IO (withFile, hSetEncoding, utf8, hSetFileSize, IOMode(WriteMode), hPutStr)
import Text.Printf (printf)


-- | Make Cards from a function, and a format string for itself and it's inverse and a range of numbers.
-- Examples:
--
-- >>> makeCards "%i + %i; %i\n" (+) "%i - %i; %i\n" 1 1
-- "1 + 1; 2\n2 - 1; 1\n2 - 1; 1\n"
-- >>> makeCards "%i * %i = %i;" (*) "%i / %i = %i;" 2 3
-- "3 * 3 = 9;2 * 3 = 6;2 * 2 = 4;9 / 3 = 3;6 / 2 = 3;4 / 2 = 2;9 / 3 = 3;6 / 3 = 2;4 / 2 = 2;"
makeCards :: String -> (Int -> Int -> Int) -> String -> Int -> Int -> String
makeCards opf op iopf start finish = popf ++ piopf
    where
        popf   = foldr (\[a, b] s -> s ++ printf  opf  a        b (op a b))  "" items
        piopf  = foldr (\[a, b] s -> s ++ printf iopf (op a b) a  b)        "" items
        items = nub $ (\a b -> sort [a,b]) <$> [start..finish] <*> [start..finish]


writeFile' :: FilePath -> String -> IO ()
writeFile' file text = withFile file WriteMode $ \f -> do
    hSetEncoding f utf8
    hSetFileSize f 0
    hPutStr f text



main :: IO ()
main = do
    writeFile' "addition_cards.txt" $ makeCards "%i + %i; %i\n" (+) "%i - %i; %i\n" 2 24
    writeFile' "multiplication_cards.txt" $ makeCards "%i × %i; %i\n" (*) "%i ÷ %i; %i\n" 2 12