[Haskell-cafe] Either instance of Monad?

Daniel Fischer daniel.is.fischer at googlemail.com
Sat Feb 26 13:28:47 CET 2011

On Saturday 26 February 2011 12:54:02, Yves Parès wrote:
> When I look at the documentation of Control.Monad.Error [1] or
> Control.Applicative [2] it is not said that it re-exports
> Control.Monad.Instances. So maybe this behaviour is normal...

I don't think so. Instances are automatically propagated, they can't be 
hidden once they're in scope. Functor, Monad, Either and (->) are all 
available in the Prelude, so unless you have NoImplicitPrelude, the 
instances ought to be in scope from any transitive dependency.
And they are in scope for me when I import Control.Monad.Error or 
Control.Applicative, so something is amiss if they're not in scope for you.

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