[Haskell] Sequencing of input and output, troubles in kdevelop

Keith Wansbrough Keith.Wansbrough at cl.cam.ac.uk
Fri Aug 27 06:53:15 EDT 2004

> "A.J. Bonnema" <abonnema at xs4all.nl> writes:
> > Why doesn't kdevelop generate code, that executes the statements in
> > order? Or should I be looking at ghc? Or is it an option I am missing?
> GHCi behaves like Hugs.  My guess would be that kdevelop attaches
> pipes for standard input and output, and GHC or whatever backend it
> uses realizes it is not talking to a terminal, and applies buffering.

In other words - if kdevelop is supposed to support the use of interactive programs in its console window, it should allocate a pty, rather than just using ordinary Unix pipes.  I would consider this a bug.

The fix for now is for you to explicitly turn off buffering:

import IO

main = do hSetBuffering stdin LineBuffering
          hSetBuffering stdout NoBuffering
          hSetBuffering stderr NoBuffering

(warning: untested code)

--KW 8-)
Keith Wansbrough <kw217 at cl.cam.ac.uk>
University of Cambridge Computer Laboratory.

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