Re: [Haskell-cafe] Why isn't hsc2hs functionality provided by ghc?

I agree that preprocessing code shouldn't be hsc2hs specific. I prefer c2hs myself. But hsc2hs is distributed with ghc, which makes it as official as a good many other parts of "modern Haskell". I also agree that making cabal-ghci work nicely would be ideal, but I don't think it can be done without either adding hooks into ghci or wrapping stdin. As Roman points out, if you use :r in ghci, cabal-ghci wouldn't pick up changes in the source file. Using ghc's support for custom preprocessors seems like a very straightforward solution: it already exists, can be used today, and isn't tied to hsc2hs. Not that this should stop anyone from working on cabal-ghci of course. On Thu, Jun 6, 2013 at 11:43 AM, Jeremy Shaw wrote:

While hsc2hs is a popular FFI preprocessor, it is not the only one. There is also greencard and a few others.

While hsc2hs can usually get the job done -- it's not clear that it is really the best choice. I think the Haskell FFI got to the point that it was 'just good enough' and then people lost interest in doing anything more. Let's face it -- working on the FFI is just not that exciting :)

So, basically, we are stuck with stuff that is 'good enough' but no so great that we want to make it official.

We can bind to C fairly easily, but for C++, Python, Ruby, Javascript, Java, etc, we have never really made much headway.

I think the efforts to make cabal-ghci work nicely could really be the best solution for now. That is more extensible, and makes it easy to solve the problem you actually care about (being able to easily load/compile .hs files) with out giving priority to any particular FFI system.

- jeremy

On Tue, Jun 4, 2013 at 9:02 PM, silly8888 wrote:

...

I was wondering today, why hasn't hsc2hs been merged with ghc so that it would be possible to add a

{-# LANGUAGE ForeignFunctionInterface #-}

at the top of a source file and then load it with ghci or compile it, without the intermediate step of calling hsc2hs? This would be exactly like the CPP extension. I don't have to call cpp manually. All I have to do is to add {-# LANGUAGE CPP #-} and then ghc will take care of the rest. This would also mean that there would be no need to have a separate file extension. Surely I must not be the first person to have that thought, so there must be a good reason why this hasn't happen yet, but what is it?

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