An IO Question from a Newbie
glynn.clements at virgin.net
Sat Sep 13 01:42:41 EDT 2003
Matt O'Connor wrote:
> Hello all. I'm new to functional programming and Haskell, but have been
> programming in C and Java for a while. I've been going through the tutorials
> and whatnot on haskell.org. I've read from the Gentle Introduction to
> Haskell about IO and some of the other stuff and I have a question about it.
> main = do putStr "Type Something: "
> str <- getLine
> putStrLn ("You typed: " ++ str)
> When compile and run this code the "Type Something: " isn't displayed until
> the putStrLn. So there is no prompt. The output looks like this.
> Type Something: You typed: s
> But if I change the putStr "Type Something: " to a putStrLn or put a \n at the
> end of the string it displays the text immediately (ie, when I want it to).
> Is there a good reason for this? Am I doing something wrong? Or do I need
> to call some kind of standard output flush? Thanks.
Yes; if you don't want a newline after the prompt, you need to use:
to flush the stream.
Glynn Clements <glynn.clements at virgin.net>
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