haskell:

...

Looks like the author of hxt has decided to support 6.12 only, at the moment.

base (>=4.2 && <5)

Ensures this will only work on the 6.12 series of compilers.

Thanks. I know.

My point is, i don't understand why hxt-8.3.2 (base >= 4 && <5) fails to install for me with:

" src/Text/XML/HXT/Parser/TagSoup.hs:292:8: Not in scope: `optLookupEntity' cabal: Error: some packages failed to install: hxt-8.3.2 failed during the building phase. The exception was: exit: ExitFailure 1 "

That looks like an error relating to the versoin of tagsoup used? -- Don

haskell:

...

That looks like an error relating to the versoin of tagsoup used?

You're right, thanks. "optLookupEntity" is defined in tagsoup-0.6, but not in tagsoup-0.8. But hxt-8.3.2 broadly requires tagsoup (>=0.6 && <1).

I am no cabal expert. What is the best solution here?

I think the best bet is to: cabal install tagsoup-0.6 --reinstrall And perhaps send the HXT maintainer a cabal patch? -- Don

Am Sonntag 24 Januar 2010 00:38:44 schrieb haskell@kudling.de:

Don Stewart hat am 24. Januar 2010 um 00:10 geschrieben:

...

haskell:

...

...

Looks like the author of hxt has decided to support 6.12 only, at the moment.

     base (>=4.2 && <5)

Ensures this will only work on the 6.12 series of compilers.

Thanks. I know.

My point is, i don't understand why hxt-8.3.2 (base >= 4 && <5) fails to install for me with:

" src/Text/XML/HXT/Parser/TagSoup.hs:292:8:      Not in scope: `optLookupEntity' cabal: Error: some packages failed to install: hxt-8.3.2 failed during the building phase. The exception was: exit: ExitFailure 1 "

That looks like an error relating to the versoin of tagsoup used?

You're right, thanks. "optLookupEntity" is defined in tagsoup-0.6, but not in tagsoup-0.8. But hxt-8.3.2 broadly requires tagsoup [http://hackage.haskell.org/package/tagsoup-0.8]  (>=0.6 && <1).

I am no cabal expert. What is the best solution here?

cabal unpack hxt-8.3.2 open hxt.cabal in kate, change the range of the required tagsoup to (>= 0.6 && < 0.7) cd hxt-8.3.2 cabal install perhaps not the _best_ solution, but quick and it usually works

Am Sunday 24 January 2010 12:24:37 schrieben Sie:

Thank you, that worked.

I wonder two things:

1) How to downgrade cabal packages? Just installing tagsoup-0.6 and removing every trace of tagsoup-0.8 somehow didn't work for me. cabal still insisted that there should be a tagsoup-0.8.

Hm, I'd think if there's no trace of tagsoup-0.8, cabal would use the installed versions to satisfy dependencies by preference. But maybe, because it sees version 0.8 available, it prefers to use the latest version available and allowed.

2) Is the commonly used version-scheming >= XYZ ideal?

No. Far from it. It's rotten, as you saw.

Maybe package maintainers should depend on exactly one version they know that works? I mean how can you guarantee, that every future version of a package will work?

You can't. Well, if you only use map, filter and arithmetics, build-depends: base is a pretty safe bet, but otherwise, adhere to the recommended dependency- scheme, build-depends: foo >= X.Y.Z && < U Specifying one exact version is too restrictive, you'll end up with everybody having umpteen versions of almost all packages installed. Minor version bumps which leave the API unchanged shouldn't break anything, small additions to the API should rarely break things, so if people adhere to http://www.haskell.org/haskellwiki/Package_versioning_policy , build-depends: foo >= X.Y.Z && < X.(Y+1) should be almost safe, build-depends: foo >= X.Y.Z && < (X+1) should be fine for relatively stable packages like base.

Minor version bumps which leave the API unchanged shouldn't break anything, http://www.haskell.org/haskellwiki/Package_versioning_policy

Neil, in this case i think, tagsoup's version shouldn't have changed from 0.6 to minor 0.8 while exported definitions such as "optLookupEntity" were removed.

Changing version number 0.6 -> 0.8 is a major release increment, not a minor one, according the package versioning policy linked to. Regards, Malcolm

Hi

...

Minor version bumps which leave the API unchanged shouldn't break anything, small additions to the API should rarely break things, so if people adhere to http://www.haskell.org/haskellwiki/Package_versioning_policy ,

Neil, in this case i think, tagsoup's version shouldn't have changed from 0.6 to minor 0.8 while exported definitions such as "optLookupEntity" were removed.

As Malcolm says, the rule is that 0.6 -> 0.8 I can do absolutely anything. If it's any consolation, I'm intending 0.9 to be perfectly compatible with 0.8. If there's anything I can do to make the hxt thing a bit easier I'm happy to do so. The change to remove optLookupEntity was necessary to support HTML 5 correctly, so I didn't really have a choice. In general I do try and keep the API as stable as possible. Thanks, Neil