lazy Printing question

Fri, 25 Jul 2003 18:02:12 +0530

On Monday 21 Jul 2003 7:21 pm, Alastair Reid wrote:
> > If I try to run the program (compiled using GHC 6), it calculates all
> > members of the list and then prints the whole list in the end. Since
> > Haskell is 'lazy' I was expecting behaviour similar to HUGS where it
> > prints the numbers as it finds them. Does this behaviour have somethi=
> > to do with the monadic IO in Haskell? I am a Haskell newbie and can't
> > even claim having understood the "gentle introduction" properly.
> My guess would be that you're seeing buffering behaviour where GHC fill=
s up
> a buffer of characters for output and flushes it every 1000, 4000 or
> whatever characters.
> IIRC correctly, buffering is off by default in Hugs but on by default i=
> GHC.
> You can turn this off with the Haskell 98 function hSetBuffering descri=
> in section 11.4.2 of the library report.

Thanks for the pointer!

Ok so I added the "hSetBuffering stdout NoBuffering" line to my main func=
tion and still got the same 'nonlazy' behaviour, or so I thought. It took=
 me some time to figure out what was going on. I am using emacs to write =
my code and I was calling a.out from inside it. Obviously it was emacs th=
at was holding back the output until the program terminated! Now I feel k=
inda stupid :-(

Anyway since I am also lazy enough to dislike switching back to the shell=
 whenever I want to test my programs, here is another question - how do I=
 make emacs give me the output AS AND WHEN it recieves it? If you are pla=
nning to say "Go read the manual" please also add some pointers to which =
part of the manual 'cos by the size of it, I'll be looking for *some* tim=
e. :-)

- AJ