[Haskell-cafe] Error when trying to use Hashable

John Ky john at gocatch.com
Mon May 12 10:05:03 UTC 2014

Hi Brandon,

I definitely have only one instance installed:

root at 26fc365ee4e6:/# ghc-pkg list | grep hash

The ubuntu system was built using this Dockerfile from using only standard
apt-get commands:

FROM ubuntu:14.04

RUN apt-get update
RUN apt-get upgrade -y
RUN apt-get install -y fakeroot curl dnsutils git golang jq openssh-client
openssh-server redis-server telnet unzip vim wget
RUN apt-get install -y ghc
RUN apt-get install -y libghc-hdbc-dev
RUN apt-get install -y libghc-hdbc-postgresql-dev
RUN apt-get install -y libghc-hdbc-sqlite3-dev
RUN apt-get install -y libghc-zeromq3-haskell-dev
RUN apt-get install -y libghc-lens-dev
RUN apt-get install -y libghc-aeson-dev libghc-aeson-pretty-dev
RUN apt-get install -y libghc-hashable-dev
RUN apt-get install -y cabal-debian
RUN apt-get install -y libghc-cryptohash-cryptoapi-dev
libghc-cryptohash-dev libghc-digest-dev libghc-hashable-dev
libghc-hashed-storage-dev libghc-hashtables-dev libghc-intern-dev
libghc-murmur-hash-dev libghc-puremd5-dev libghc-skein-dev
libghc-static-hash-dev libghc-unordered-containers-dev
RUN apt-get clean



On 12 May 2014 11:03, Brandon Allbery <allbery.b at gmail.com> wrote:

> On Sun, May 11, 2014 at 8:58 PM, John Ky <john at gocatch.com> wrote:
>> I have some code that compiles when running on GHC on OS X, but not on
>> Ubuntu:
>>     No instance for (hashable-
>>                        (GHC.Generics.Rep Point))
>>       arising from a use of
>> `hashable-$gdmhashWithSalt'
>>     Possible fix:
>>       add an instance declaration for
>>       (hashable-
>>          (GHC.Generics.Rep Point))
>>     In the expression:
>>       (hashable-$gdmhashWithSalt)
>>     In an equation for `hashWithSalt':
>>         hashWithSalt
>>           = (hashable-$gdmhashWithSalt)
>>     In the instance declaration for `Hashable Point'
> The fully qualified (with package name/version) typeclass makes me think
> you have multiple versions of the hashable package installed, and the one
> your source is using is different from one pulled in by something else.
> ghc makes it dangerous to have multiple versions of a package installed.
> Use `ghc-pkg list` to make sure you have only one; if there is one in the
> global section and another in the local section, remove the local one and
> reinstall anything broken by that with `cabal install $thepackage
> --constraint='hashable installed'`.
> --
> brandon s allbery kf8nh                               sine nomine
> associates
> allbery.b at gmail.com
> ballbery at sinenomine.net
> unix, openafs, kerberos, infrastructure, xmonad
> http://sinenomine.net

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