On Mon, Oct 5, 2015 at 9:02 PM, Erik Hesselink <hessel...@gmail.com> wrote:
> On 5 October 2015 at 20:58, Sven Panne <svenpa...@gmail.com> wrote: > > 2015-10-05 17:09 GMT+02:00 Gershom B <gersh...@gmail.com>: > >> > >> [...] As for libraries, it has been pointed out, I believe, that without > >> CPP one can write instances compatible with AMP, and also with AMP + > MRP. > >> One can also write code, sans CPP, compatible with pre- and post- AMP. > [...] > > > > Nope, at least not if you care about -Wall: If you take e.g. (<$>) which > is > > now part of the Prelude, you can't simply import some compatibility > module, > > because GHC might tell you (rightfully) that that import is redundant, > > because (<$>) is already visible through the Prelude. So you'll have to > use > > CPP to avoid that import on base >= 4.8, be it from it Data.Functor, > > Control.Applicative or some compat-* module. And you'll have to use CPP > in > > each and every module using <$> then, unless I miss something obvious. > > AFAICT all transitioning guides ignore -Wall and friends... > > Does the hack mentioned on the GHC trac [1] work for this? It seems a > bit fragile but that page says it works and it avoids CPP. > No it doesn't, if you also don't want closed import lists (which you should).
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