#1354: Interactive I/O with ghc doesn't prompt until after reading
--------------------------------+-------------------------------------------
Reporter: [EMAIL PROTECTED] | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: Prelude | Version: 6.2
Severity: normal | Keywords: interactive stdio late prompt
Difficulty: Unknown | Os: Multiple
Testcase: | Architecture: Multiple
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My students complained that the interactive program they were to write
using
Haskell would not issue its first prompt until after the first line of
input
had been entered. I enclose a tiny Haskell program that exhibits this
behaviour in 6.2 (SPARC Solaris) and 6.4 (Intel Linux) and am told that it
also happens in 6.6. I also show that it works fine in Hugs, HBC, and
NCH98.
Script started on Tue 15 May 2007 02:11:26 PM NZST
f% cat -n kcl.hs
1 main =
2 putStr "Enter a line:" >>
3 putChar ' ' >>
4 getLine >>= \a ->
5 putStrLn a >>
6 putStrLn a
f% uname -a
SunOS frege 5.9 Generic_112233-04 sun4u sparc SUNW,Sun-Blade-100
f% hugs98
[snip]
|| || Version: February 2001 _________________________________________
Haskell 98 mode: Restart with command line option -98 to enable extensions
Reading file
"/home/users/okeefe_r/quasar/hugs98/shared/hugs/lib/Prelude.hs":
[snip]
Prelude> :load kcl
Reading file "kcl.hs":
[snip]
kcl.hs
Main> main
Enter a line: Foo!
Foo!
Foo!
Main> [Leaving Hugs]
f% rm a.out
f% nhc98 -o a.out kcl.hs
f% a.out
Enter a line: Foo!
Foo!
Foo!
f% rm a.out
f% hbc -o a.out kcl.hs
f% a.out
Enter a line: Foo!
Foo!
Foo!
f% rm a.out
f% ghc --version
The Glorious Glasgow Haskell Compilation System, version 6.2
f% ghc kcl.hs
f% a.out
Foo!
Enter a line: Foo!
Foo!
f% [[ftp kcl.hs to bling]]
f% ssh bling
[snip]
b% uname -a
Linux oucs816.otago.ac.nz 2.6.19-1.2911.fc6 #1 SMP Sat Feb 10 15:51:47 EST
2007 i686 i686 i386 GNU/Linux
b% hugs
b% hugs
[snip]
|| || Version: November 2002 _________________________________________
[snip]
Prelude> :load kcl
Reading file "kcl.hs":
Hugs session for:
/usr/local/lib/hugs/lib/Prelude.hs
kcl.hs
Main> main
Enter a line: Bar!
Bar!
Bar!
Main> [Leaving Hugs]
b% rm a.out
b% ghc --version
The Glorious Glasgow Haskell Compilation System, version 6.4
b% ghc kcl.hs
b% ./a.out
Bar!
Enter a line: Bar!
Bar!
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/1354>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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