Question

我正试图制定一个方案,读到用户提供的数字,然后印制。在我印刷时,数字必须呈立体字,但该代码给我留下一个大错:

main = do
{
       putStrLn "Please enter the number"
       number <- getLine
       putStrLn "The num is:" ++ show (read number:: Int)
}

Answer 1

If you use brackets in your do statement, you have to use semicolons. Also, the last line should be putStrLn $ "The num is:" ++ show (read number :: Int)

因此,你有两个选择:

main = do
{
   putStrLn "Please enter the number";
   number <- getLine;
   putStrLn $ "The num is:" ++ show (read number:: Int)
}

or:

main = do
   putStrLn "Please enter the number"
   number <- getLine
   putStrLn $ "The num is:" ++ show (read number:: Int)

我所看到的几乎所有法典都使用了第二版,但它们都有效。请注意,在第二版中,白天空间变得巨大。

Answer 2

Haskell recognizes the Tab character and your program could be failing because of that. If you re using Tabs, change them to whitespaces.

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