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

[John Lato]

cabal-dev ghci does work with hsc2hs, but only because it doesn't interpret
your source.  Rather, cabal-dev ghci loads ghci using the sandbox install
of your package, which is less useful for a variety of reasons.

Aside from that detail, I wouldn't gain any benefit from having this
feature built in to ghci instead of accessing ghci via cabal (or
cabal-dev).  cabal seems like a better location, and it's aware of several
preprocessors already.



On Wed, Jun 5, 2013 at 12:00 PM, Jason Dagit <dagitj at gmail.com> wrote:

> On Tue, Jun 4, 2013 at 8:45 PM, John Lato <jwlato at gmail.com> wrote:
> > On Wed, Jun 5, 2013 at 10:15 AM, Ivan Lazar Miljenovic
> > <ivan.miljenovic at gmail.com> wrote:
> >>
> >> On 5 June 2013 12:02, silly8888 <silly8888 at gmail.com> 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?
> >>
> >> Isn't this done automatically when you have files with the .hsc
> extension?
> >
> >
> > cabal handles this transparently, but not ghc.  It's frustrating when you
> > want to develop a project with ghci.
> >
> > I don't think it's a good idea to merge hsc2hs syntax into Haskell files.
> > In particular, it's often useful to inspect the intermediate .hs file
> > produced by hsc2hs during development or debugging.  Also it would
> > complicate ghc's parser, etc...
> >
> > My preferred solution would be to have ghc/ghci automatically run hsc2hs
> > (support c2hs also?) when necessary.  But so long as it's handled
> > automatically, I wouldn't be particularly bothered by the implementation.
>
> How about having a `ghci` command for cabal? Or does the automatic
> requirement really need to be part of ghc to work the way you want?
>
> (BTW, cabal-dev does have a `ghci` command, but I haven't tested to
> see if it does the hsc -> hs conversion.)
>
> Jason
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.haskell.org/pipermail/haskell-cafe/attachments/20130605/47e58708/attachment.htm>