Hello all, I am currently playing with the new cadre of failure libraries, and I'm trying to figure out how to use the monadic version of Failure while also getting the Try typeclass, which appears to be the standardized mechanism for marshalling values from specific monads into the failure monad. Unfortunately, it only seems to be defined when I import Control.Failure, and this module is fairly incompatible with Control.Monad.Failure, as demonstrated by this GHCI transcript: ezyang@javelin:~/Documents/tmr$ ghci Prelude> :m +Control.Failure Prelude Control.Failure> :m +Control.Monad.Failure Prelude Control.Failure Control.Monad.Failure> :t failure <interactive>:1:0: Ambiguous occurrence `failure' It could refer to either `Control.Failure.failure', imported from Control.Failure or `Control.Monad.Failure.failure', imported from Control.Monad.Failure I'm using MTL, which might be the reason why there's all sorts of unhappiness. :-) Cheers, Edward
On Wed, Dec 30, 2009 at 5:52 PM, Edward Z. Yang
Hello all,
I am currently playing with the new cadre of failure libraries, and I'm trying to figure out how to use the monadic version of Failure while also getting the Try typeclass, which appears to be the standardized mechanism for marshalling values from specific monads into the failure monad. Unfortunately, it only seems to be defined when I import Control.Failure, and this module is fairly incompatible with Control.Monad.Failure, as demonstrated by this GHCI transcript:
ezyang@javelin:~/Documents/tmr$ ghci Prelude> :m +Control.Failure Prelude Control.Failure> :m +Control.Monad.Failure Prelude Control.Failure Control.Monad.Failure> :t failure
<interactive>:1:0: Ambiguous occurrence `failure' It could refer to either `Control.Failure.failure', imported from Control.Failure or `Control.Monad.Failure.failure', imported from Control.Monad.Failure
I'm using MTL, which might be the reason why there's all sorts of unhappiness. :-)
Cheers, Edward _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Why are you importing both Control.Failure and Control.Monad.Failure when the latter just re-exports the former? Are you using the latest versions of the two packages? Try importing just Control.Monad.Failure.MTL; that provides the MTL failure instances and also re-exports Control.Failure. Alex
Excerpts from Alexander Dunlap's message of Thu Dec 31 00:06:58 -0500 2009:
Why are you importing both Control.Failure and Control.Monad.Failure when the latter just re-exports the former? Are you using the latest versions of the two packages? Try importing just Control.Monad.Failure.MTL; that provides the MTL failure instances and also re-exports Control.Failure.
That's correct. I imported both when Control.Monad.Failure.MTL failed to expose try: ezyang@javelin:~/Dev/wizard$ ghci Prelude> :m +Control.Monad.Failure.MTL Prelude Control.Monad.Failure.MTL> :t try <interactive>:1:0: Not in scope: `try' Which, doesn't really seem like it should be the case. Cheers, Edward
Edward,
What version of the packages are you using? Can you give the output of:
ghc-pkg list|grep failure
Michael
On Thu, Dec 31, 2009 at 7:11 AM, Edward Z. Yang
Excerpts from Alexander Dunlap's message of Thu Dec 31 00:06:58 -0500 2009:
Why are you importing both Control.Failure and Control.Monad.Failure when the latter just re-exports the former? Are you using the latest versions of the two packages? Try importing just Control.Monad.Failure.MTL; that provides the MTL failure instances and also re-exports Control.Failure.
That's correct. I imported both when Control.Monad.Failure.MTL failed to expose try:
ezyang@javelin:~/Dev/wizard$ ghci Prelude> :m +Control.Monad.Failure.MTL Prelude Control.Monad.Failure.MTL> :t try
<interactive>:1:0: Not in scope: `try'
Which, doesn't really seem like it should be the case.
Cheers, Edward _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Excerpts from Michael Snoyman's message of Thu Dec 31 00:43:52 -0500 2009:
What version of the packages are you using? Can you give the output of:
ghc-pkg list|grep failure
Sure thing: (control-monad-failure-0.4), (control-monad-failure-0.5.0), control-monad-failure-mtl-0.5.0, cpphs-1.8, cpphs-1.9, failure-0.0.0.1, happstack-0.3.2, happstack-data-0.3.3 Additionally: ezyang@javelin:~$ cabal upgrade failure Resolving dependencies... No packages to be installed. All the requested packages are already installed. If you want to reinstall anyway then use the --reinstall flag. Cheers, Edward
On Wed, Dec 30, 2009 at 10:54 PM, Edward Z. Yang
Excerpts from Michael Snoyman's message of Thu Dec 31 00:43:52 -0500 2009:
What version of the packages are you using? Can you give the output of:
ghc-pkg list|grep failure
Sure thing:
(control-monad-failure-0.4), (control-monad-failure-0.5.0), control-monad-failure-mtl-0.5.0, cpphs-1.8, cpphs-1.9, failure-0.0.0.1, happstack-0.3.2, happstack-data-0.3.3
Additionally:
ezyang@javelin:~$ cabal upgrade failure Resolving dependencies... No packages to be installed. All the requested packages are already installed. If you want to reinstall anyway then use the --reinstall flag.
Cheers, Edward
Upgrade to control-monad-failure-mtl 0.6.0 and control-monad-failure 0.6.0. Alex
I upgraded, but now both Control.Monad.Failure and Control.Monad.Error claim to be exporting "Error". Is this correct, and if so, which one should I hide? Cheers, Edward
Excerpts from Edward Z. Yang's message of Fri Jan 01 13:27:49 -0500 2010:
I upgraded, but now both Control.Monad.Failure and Control.Monad.Error claim to be exporting "Error". Is this correct, and if so, which one should I hide?
Sorry my bad; I should have been importing Control.Monad.Failure.MTL. The error has gone away. Cheers, Edwadrd
I think you need to run "cabal update"
On Thu, Dec 31, 2009 at 8:54 AM, Edward Z. Yang
Excerpts from Michael Snoyman's message of Thu Dec 31 00:43:52 -0500 2009:
What version of the packages are you using? Can you give the output of:
ghc-pkg list|grep failure
Sure thing:
(control-monad-failure-0.4), (control-monad-failure-0.5.0), control-monad-failure-mtl-0.5.0, cpphs-1.8, cpphs-1.9, failure-0.0.0.1, happstack-0.3.2, happstack-data-0.3.3
Additionally:
ezyang@javelin:~$ cabal upgrade failure Resolving dependencies... No packages to be installed. All the requested packages are already installed. If you want to reinstall anyway then use the --reinstall flag.
Cheers, Edward
participants (3)
-
Alexander Dunlap -
Edward Z. Yang -
Michael Snoyman