An IO Question from a Newbie
Hal Daume III
hdaume at ISI.EDU
Fri Sep 12 17:18:22 EDT 2003
This is a buffering problem. Use hSetBuffering to fix this (see Chapter 3
in YAHT -- www.isi.edu/~hdaume/htut/). Alternatively, use:
> main = do putStrLn "Type Something:"
in which case the "Ln" part will force it to be printed.
On Fri, 12 Sep 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.
> Oh, I'm using ghc.
Hal Daume III | hdaume at isi.edu
"Arrest this man, he talks in maths." | www.isi.edu/~hdaume
More information about the Haskell-Cafe