自动生成计算题

最近老师总是让出一些计算题，于是用haskell写了一个。

-- file: make_math2.hs
-- 出n道三个参数的加法
-- 452 + 990 + 130=1572
-- 使用方法: gs n x y
--              n 表示需要多少道题
--              x 表示最小值
--              y 表示最大值
--       比如 gs 10 100 999 表示出10道 加法
--       gs'会过滤掉被10整除的数字，这样难一点

import System.Random
import System.IO.Unsafe

drawInt :: Int -> Int -> IO Int
drawInt x y = getStdRandom (randomR (x,y))

random_list :: (Eq a, Num a) => a -> Int -> Int -> IO [Int]
random_list 0 _ _ = return []
random_list n x y = do
    a <- drawInt x y
    rest <- (random_list (n-1) x y)
    return (a : rest)


math_practice n x y  = zip [1..] $ map trans_formula (mix_list (init_val (n*3) x y ))
    where mix_list [] = []
          mix_list (x:y:z:xs) = (x,y,z) : mix_list xs 
          init_val n x y = unsafePerformIO $ random_list n x y

          trans_formula (x,y,z) = ((add_str x y z) , (add_str' x y z))

          add_str x y z = show x ++ " + " ++ show y  ++ " + " ++ show z ++ "= "
          add_str' x y z = show x ++ " + " ++ show y ++  " + "  ++ show z ++ "=" ++ show (x+y+z)


math_practice' n x y  = zip [1..] $ map trans_formula $ mix_list 
                $ take (n*3) $ filter (\x -> (x `mod` 10) /= 0) $ init_val (n*9) x y
    where mix_list [] = []
          mix_list (x:y:z:xs) = (x,y,z) : mix_list xs 
          init_val n x y = unsafePerformIO $ random_list n x y

          trans_formula (x,y,z) = ((add_str x y z) , (add_str' x y z))

          add_str x y z = show x ++ " + " ++ show y  ++ " + " ++ show z ++ "= "
          add_str' x y z = show x ++ " + " ++ show y ++  " + "  ++ show z ++ "=" ++ show (x+y+z)
gs n x y = do
    mapM_ putStrLn [ show a ++ ". " ++ b| (a,(b,c))<-temp_list]
    putStrLn " "
    mapM_ putStrLn [ show a ++ ". " ++ c| (a,(b,c))<-temp_list]
    where temp_list = math_practice' n x y

gs' n x y = do
    mapM_ putStrLn [ b| (a,(b,c))<-temp_list]
    putStrLn " "
    where temp_list = math_practice' n x y

{-main = do-}
    {-gs 10 100 999-}

使用的例子

> gs 10 10 99
1. 94 + 79 + 26= 
2. 34 + 65 + 73= 
3. 88 + 29 + 24= 
4. 54 + 93 + 29= 
5. 32 + 79 + 82= 
6. 24 + 55 + 67= 
7. 46 + 16 + 64= 
8. 43 + 39 + 84= 
9. 38 + 89 + 62= 
10. 91 + 51 + 83= 
 
1. 94 + 79 + 26=199
2. 34 + 65 + 73=172
3. 88 + 29 + 24=141
4. 54 + 93 + 29=176
5. 32 + 79 + 82=193
6. 24 + 55 + 67=146
7. 46 + 16 + 64=126
8. 43 + 39 + 84=166
9. 38 + 89 + 62=189
10. 91 + 51 + 83=225