Ketil Malde writes:
I have a program that makes use of the applicative instance for Either String. I used to define these instances locally, but at some point, they became part of Control.Applicative. I have limited the dependencies to 'base >= 4', but apparently, some version 4s of base include this instance, some do not, and it causes problems for people trying to compile the program.
Is there any information, or otherwise accessible source specifying exactly when this was changed, so that I can have more precise dependencies?
base is released with GHC, so the info is in the release notes for a major GHC release (library interfaces aren't allowed to change in minor releases): http://www.haskell.org/ghc/docs/7.0.1/html/users_guide/release-7-0-1.html#id... 1.5.10.2. base * Version number 4.3.0.0 (was 4.2.0.2) [...] * There are now Applicative, Monad and MonadFix instances for Either.