Don Stewart writes:

arnaud.oqube:

...

Hello, I have a strange issue which sprang today out of nowhere. When I load a certain file using bytestring package in Ghci using emacs, I got the following error:

Couldn't match expected type `Data.ByteString.Internal.ByteString' against inferred type `bytestring-0.9.1.4:Data.ByteString.Internal.ByteString' In the second argument of `hPutStrLn', namely `(fromString msgs)' In a stmt of a 'do' expression: hPutStrLn cnx (fromString msgs)

The same file compiles fine on the command-line. I have a single installation of haskell platform, using ghc 6.10.4, on windows XP.

Looks like you might have two versions of bytestring installed (ghc-pkg list bytestring) and are attempting to combine them. The diamond dependency problem.

* delete the old version (ghc-pkg unregister)

Isn't the old version likely to be the one that comes with GHC and hence shouldn't be touched? -- Ivan Lazar Miljenovic Ivan.Miljenovic@gmail.com IvanMiljenovic.wordpress.com

I did: ghc-pkg unregister bytestring-0.9.1.6 then restarted emacs and it works now. Don't now if ther weill be side-effects on other packages... Thanks for the tip. arnaud On Thu, Jun 10, 2010 at 6:15 AM, Arnaud Bailly wrote:

Yes, I have two versions installed , 0.9.1.4 and 0.9.1.6. Here is the output of ghc-pkg -l:

d:/Program Files/Haskell Platform/2009.2.0.2\package.conf:    Cabal-1.6.0.3, GLUT-2.1.1.2, HSlim-0.1, HTTP-4000.0.6,    HUnit-1.2.0.3, OpenGL-2.2.1.1, QuickCheck-1.2.0.0,    QuickCheck-2.1.0.3, Win32-2.2.0.0, array-0.2.0.0, base-3.0.3.1,    base-4.1.0.0, bytestring-0.9.1.4, bytestring-0.9.1.6,    cgi-3001.1.7.1, containers-0.2.0.1, directory-1.0.0.3,    (dph-base-0.3), (dph-par-0.3), (dph-prim-interface-0.3),    (dph-prim-par-0.3), (dph-prim-seq-0.3), (dph-seq-0.3),    extensible-exceptions-0.1.1.0, fgl-5.4.2.2, filepath-1.1.0.2,    (ghc-6.10.4), ghc-prim-0.1.0.0, haddock-2.4.2, haskell-src-1.0.1.3,    haskell98-1.0.1.0, hpc-0.5.0.3, html-1.0.1.2, integer-0.1.0.1,    mtl-1.1.0.2, network-2.2.1.4, old-locale-1.0.0.1, old-time-1.0.0.2,    packedstring-0.1.0.1, parallel-1.1.0.1, parsec-2.1.0.1,    pretty-1.0.1.0, process-1.0.1.1, random-1.0.0.1,    regex-base-0.72.0.2, regex-compat-0.71.0.1, regex-posix-0.72.0.3,    rts-1.0, stm-2.1.1.2, syb-0.1.0.1, template-haskell-2.3.0.1,    time-1.1.2.4, utf8-string-0.3.6, xhtml-3000.2.0.1, zlib-0.5.0.0

However, I tried to force the version I use to be 0.9.1.6 and it does not work as ghc itself seems to require 0.9.1.4, as pointed out by Ivan. I did not try to remove one or the other however.

Arnaud

On Thu, Jun 10, 2010 at 12:13 AM, Ivan Lazar Miljenovic wrote:

...

Don Stewart writes:

...

arnaud.oqube:

...

Hello, I have a strange issue which sprang today out of nowhere. When I load a certain file using bytestring package in Ghci using emacs, I got the following error:

Couldn't match expected type `Data.ByteString.Internal.ByteString'            against inferred type `bytestring-0.9.1.4:Data.ByteString.Internal.ByteString'     In the second argument of `hPutStrLn', namely `(fromString msgs)'     In a stmt of a 'do' expression: hPutStrLn cnx (fromString msgs)

The same file compiles fine on the command-line. I have a single installation of haskell platform, using ghc 6.10.4, on windows XP.

Looks like you might have two versions of bytestring installed (ghc-pkg list bytestring) and are attempting to combine them. The diamond dependency problem.

    * delete the old version (ghc-pkg unregister)

Isn't the old version likely to be the one that comes with GHC and hence shouldn't be touched?

-- Ivan Lazar Miljenovic Ivan.Miljenovic@gmail.com IvanMiljenovic.wordpress.com