putStrLn看到太多的参数haskell

Question

我有一个putStrLn，它在下一行看到一个函数，因此无法正确编译。

if director == "" then
        putStrLn "Please enter a directors name"
        startFunctional 5 userName database --This line is seen as an argument for the putStrLn
    else do
        *etc*

我尝试使用括号来隔离字符串，但这会引发相同的错误。

错误讯息：

The function `putStrLn' is applied to five arguments, but its type `String -> IO ()' has only one

Answer 1

您是否可能错过do阻止？

if director == "" 
then do
    putStrLn "Please enter a directors name"
    startFunctional 5 userName database
else do
    *etc*

另外，请尝试调整then块的else和if个关键字。