示例代码:
fac :: Int → Int
fac 0 = 1
fac n = n * fac (n-1)
main = do
putStrLn show fac 10
错误:
Couldnt match expected type 'String'
against inferred type 'a -> String'
In the first argument of 'putStrLn', namely 'show'
In the expression: putStrLn show fac 10