Prelude.OldIO

IO Requests and responses

data IORequest

Constructors

Print String

PrintChar Char

GetLine

ReadFile FilePath

WriteToFile FilePath String

Exit

data IOResponse

Constructors

Success

FileContents String

ConsoleLine String

Instances

NFData IOResponse

run :: ([IOResponse] -> [IORequest]) -> IO ()

Other convenient operators

(.) :: (b -> c) -> (a -> b) -> a -> c

Function composition.

trace :: String -> a -> a

The trace function outputs the trace message given as its first argument, before returning the second argument as its result.

For example, this returns the value of f x but first outputs the message.

 trace ("calling f with x = " ++ show x) (f x)

The trace function should only be used for debugging, or for monitoring execution. The function is not referentially transparent: its type indicates that it is a pure function but it has the side effect of outputting the trace message.