不在haskell中编译printf

Question

伙计们请告诉我为什么这不是编译

putStrLn("The average number of fans for the films of " ++ actor ++ " is : " ++ printf "%.2f\n" (show(countAveFans actor testDatabase))

它很简单，但我不能想为什么它不起作用。我尝试将整个事物转换为字符串并打印出2小数点。谢谢

Answer 1

您需要向RealFloat提供String而不是printf，因此请取消对show的调用：

putStrLn $ "The average number of fans for the films of " ++ actor ++ " is : " ++ (printf "%.2f\n" $ countAveFans actor testDatabase)