Field label bug?
Is this a bug with ghc-4.04 or just a "feature" of Haskell 98 that I was
unaware of? I get a parse error with the following code:
data Point = Pt {pointx, pointy :: Float}
abs (Pt {pointx, pointy}) = sqrt (pointx*pointx + pointy*pointy)
It doesn't like the `,' on the second line. If I change it to:
abs (Pt {pointx=pointx, pointy=pointy}) = sqrt (pointx*pointx +
pointy*pointy)
It compiles fine.
This is on Solaris 2.5, in case it matters.
- Michael Hobbs
RE: Problems with GHC 4.04 binary package under i386 Linux
Simon Marlow is away till next week, so I'm afraid you won't get any help till then. Sorry. Simon > -Original Message- > From: Mark Utting > Sent: Monday, August 09, 1999 9:49 PM > To: [EMAIL PROTECTED] > Cc: [EMAIL PROTECTED] > Subject: Problems with GHC 4.04 binary package under i386 Linux > > > > I am having trouble installing the latest GHC binary bundle for > Linux (4.04). I've tried it under Redhat Linux 5.02, and a > Slackware Linux distribution (kernel = 2.0.35), with the same results. > I did not have these problems with GHC 4.02...
Instance bug
Here one of my favourite bugs in larger projects (IIRC, this
has partly been reported by me in the "Importing, hiding, and
exporting" thread):
-- A.hs -
module A where
data Foo = Foo -- Typo! Forgot "deriving Show"
-- B.hs -
module B where
import A
data Bar = Bar Foo deriving Show
data Baz = Baz Int deriving Show
-- Main.hs --
import A
import B
main :: IO ()
main = print (Bar Foo, Baz 42)
-
panne@jeanluc:~ > ghc -Wall -O -c A.hs
ghc: module version changed to 1; reason: no old .hi file
panne@jeanluc:~ > ghc -Wall -O -c B.hs
ghc: module version changed to 1; reason: no old .hi file
[??? Why does B compile? And why is Baz's Show instance not in B.hi? ]
panne@jeanluc:~ > ghc -Wall -O -c Main.hs
Main.hs:4:
No instance for `Show Baz' arising from use of `print' at Main.hs:4
Main.hs:4:
No instance for `Show Bar' arising from use of `print' at Main.hs:4
This one drove me mad several times, looking at the completely
wrong place (i.e. B.hs).%-{
Cheers,
Sven
--
Sven PanneTel.: +49/89/2178-2235
LMU, Institut fuer Informatik FAX : +49/89/2178-2211
LFE Programmier- und Modellierungssprachen Oettingenstr. 67
mailto:[EMAIL PROTECTED]D-80538 Muenchen
http://www.pms.informatik.uni-muenchen.de/mitarbeiter/panne
Typechecker buglet
The typo in the following module causes ghc to crash:
--
module Foo where
data Bar = Bar { flag :: Bool }
data State = State { bar :: Bar, baz :: Float }
display :: State -> IO ()
display (State{ bar = Bar { flag = f, baz = b }}) = print (f,b)
-- Typo! The line above should better be:
-- display (State{ bar = Bar { flag = f }, baz = b }) = print (f,b)
--
panne@jeanluc:~ > ghc -Wall -O -c Foo.hs
panic! (the `impossible' happened):
tcLookupValue: b{-r4n-}
Please report it as a compiler bug to [EMAIL PROTECTED]
Done! :o)
Cheers,
Sven
--
Sven PanneTel.: +49/89/2178-2235
LMU, Institut fuer Informatik FAX : +49/89/2178-2211
LFE Programmier- und Modellierungssprachen Oettingenstr. 67
mailto:[EMAIL PROTECTED]D-80538 Muenchen
http://www.pms.informatik.uni-muenchen.de/mitarbeiter/panne
Re: Field label bug?
On Mon, Aug 16, 1999 at 16:40:30 -0500, Michael Hobbs wrote:
> Is this a bug with ghc-4.04 or just a "feature" of Haskell 98 that I was
> unaware of? I get a parse error with the following code:
>
> data Point = Pt {pointx, pointy :: Float}
> abs (Pt {pointx, pointy}) = sqrt (pointx*pointx + pointy*pointy)
*hmm* at least hugs also complains:
ERROR "recs.hs" (line 2): Haskell 98 does not support missing field bindings
But you can also do:
\begin{code}
abs (Pt pointx pointy) = sqrt (pointx*pointx + pointy*pointy)
\end{code}
if you don't want to mention field names...
Cheers,
Michael
--
Today, signature's out...
(no subject)
Hello friends: Thanks for making GHC available. I regret to report the following installation problem. Yours, Tim Sauerwein [EMAIL PROTECTED] -- Windows 98 Cygwin B20 GHC 4.03, Install Shield Version Everything unpacked successfully. Configure produced: creating cache ./config.cache checking host system type... i386-unknown-mingw32 checking target system type... i386-unknown-mingw32 checking build system type... i386-unknown-mingw32 Which we'll further canonicalise into: i386-unknown-mingw32 checking for perl... /BIN/perl checking if `#!/BIN/perl' works in shell scripts It does! checking for a BSD compatible install... /CYGNUS/CYGWIN~1/H-I586~1/BIN/install -c checking whether ln -s works... yes checking for sed... /CYGNUS/CYGWIN~1/H-I586~1/BIN/sed checking for gcc... gcc checking whether the C compiler (gcc -mno-cygwin ) works... yes checking whether the C compiler (gcc -mno-cygwin ) is a cross-compiler... no checking whether we are using GNU C... yes checking whether gcc accepts -g... yes checking whether you have an ok gcc... yes checking how to run the C preprocessor... gcc -E checking how to invoke GNU cpp directly... C:/CYGNUS/CYGWIN~1/H-I586~1/BIN/../lib/gcc-lib/i586-cygwin32/egcs-2.91.57/cpp -iprefix C:/CYGNUS/CYGWIN~1/H-I586~1/BIN/../lib/gcc-lib/i586-cygwin32/egcs-2.91.57/ updating cache ./config.cache creating ./config.status creating Makefile Configuration done, ready to either 'make install' or 'make in-place', followed by 'make install-docs'. (see README and INSTALL files for more info.) make in-place produced: make --unix config-pkgs bindir=/ghc/ghc-4.03/bin/i386-unknown-mingw32/ghc-4.03 libdir=/ghc/ghc-4.03/lib/i386-unknown-mingw32 datadir=/ghc/ghc-4.03/share/ghc-4.03 Configuring ghc, version 4.03, on i386-unknown-mingw32 ... Creating a configured version of ghc-4.03 .. cannot create bin/i386-unknown-mingw32/ghc-4.03/ghc-4.03: directory nonexistent make[1]: *** [config-pkgs] Error 2 make: *** [in-place] Error 2
RE: Field label bug?
"Punning" was removed (in my view this was a mistake) in Haskell 98.
That's why neither GHC nor Hugs accepts it.
Simon
> -Original Message-
> From: Michael Hobbs
> Sent: Monday, August 16, 1999 10:41 PM
> Cc: [EMAIL PROTECTED]
> Subject: Field label bug?
>
>
> Is this a bug with ghc-4.04 or just a "feature" of Haskell 98
> that I was
> unaware of? I get a parse error with the following code:
>
> data Point = Pt {pointx, pointy :: Float}
> abs (Pt {pointx, pointy}) = sqrt (pointx*pointx + pointy*pointy)
>
> It doesn't like the `,' on the second line. If I change it to:
>
> abs (Pt {pointx=pointx, pointy=pointy}) = sqrt (pointx*pointx +
> pointy*pointy)
>
> It compiles fine.
> This is on Solaris 2.5, in case it matters.
>
> - Michael Hobbs
>
