Proposal: NoImplicitPreludeImport

Johan Tibell johan.tibell at
Tue May 28 17:58:29 CEST 2013

On Tue, May 28, 2013 at 8:23 AM, Ian Lynagh <ian at> wrote:

> Dear Haskellers,
> I have made a wiki page describing a new proposal,
> NoImplicitPreludeImport, which I intend to propose for Haskell 2014:
> What do you think?

-1 for me.

Breaking every single Haskell module for some namespace reorganization
doesn't seem worth it. I don't think alternative Prelused (one of the
justifications) is a good idea to begin with, as programmers will have to
first understand which particular version of e.g. map this module uses,
instead of knowing it's the same one as every other module uses.

Changes like this will likely cause years worth of pain e.g. see the Python
2/Python 3 failure.

The likely practical result of this is that every module will now read:

module M where

#if MIN_VERSION_base(x,y,z)
import Prelude
import Data.Num
import Control.Monad

for the next 3 years or so.

-- Johan
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