Try to allow for someone to execute in Validation if they want

[tel]

@bitemyapp wants to be able to use http://hackage.haskell.org/package/validation but that takes a dependency on lens. I am using that type (called Internal.Collect) so perhaps I could expose a general interface instead of using Validation instead.

[bitemyapp]

General interface ~ typeclass or direct final encoding?

[tel]

Most likely direct in order to avoid extra names/exports. Or maybe I'll use Control.Monad.Except.