如何重用函数以在 Haskell 中有效地“循环”

Question

I've got a short interaction dialog where the computer asks for a number, and if it's smaller than 77, it states it's too small and to try again.

The issue I have on hand is probably something simple, but as I'm relatively new I can't seem to get it too work, nor can find any related issues online.

import Text.Read

myread :: IO Int
myread  = do putStr "Please enter a number: "             
             x <- readLn             
             return x

isItLarge :: IO()
isItLarge = do
              result <- myread;
              if result < 77 then putStrLn "Tiny, try again!";
                                  myread
                             else putStrLn "Massive!";
               
               

In my logic, calling myread should revert it back to the top and allow you to continue until n > 77 is reached. Any help would be appreciated:)

Answer 1

对于你的问题的具体方案，最简单的方法是只需更换你的第二呼叫myread用递归调用isItLarge 。