Re: [Haskell-cafe] Portability of Safe Haskell packages

* Herbert Valerio Riedel [2012-11-24 00:06:44+0100]

Roman Cheplyaka writes:

...

It has been pointed out before that in order for Safe Haskell to be useful, libraries (especially core libraries) should be annotated properly with Safe Haskell LANGUAGE pragmas.

However, that would make these libraries unusable with alternative Haskell implementations, even if otherwise they these libraries are Haskell2010.

To quote the standard:

If a Haskell implementation does not recognize or support a particular language feature that a source file requests (or cannot support the combination of language features requested), any attempt to compile or otherwise use that file with that Haskell implementation must fail with an error.

Should it be advised to surround safe annotations with CPP #ifs? Or does anyone see a better way out of this contradiction?

...but IIRC CPP isn't part of Haskell2010, or is it?

It isn't indeed. But: 1) it's a very basic extension which is supported by (almost?) all existing implementations; or 2) if you want to be 100% Haskell2010, you can name your file *.cpphs and let Cabal do preprocessing. 1) is a compromise and 2) is not very practical, so I'm eager to hear other alternatives. Roman