On Sun, Feb 22, 2009 at 8:15 AM, John Meacham <j...@repetae.net> wrote:
> On Sun, Feb 22, 2009 at 03:36:34PM +0100, Peter Verswyvelen wrote: > > Would it be possible to separate the frontend (Haskell to Core) and > backend > > (Core to machine code) from the Haskell compilers (requiring a standard > Core > > language?) > > I'm not sure how many extensions required a change to the Core language. > > Well, it depends on what you mean by 'core'. If you mean a desugared > version of haskell, I think such a front end could be quite useful. By the way, coming up pretty soon, I will need a desugared *annotated*Haskell for Dana. If anybody has something like this in the works, I'd love to help with it. If it does not exist by the time I need it, I will make it, so if anyone is interested in working on it with me, let me know :-) Luke > in > particular, I'd like to see a standalone implementation of template > haskell. If you mean something lower level, as in the ghc core > intermediate language the compiler uses internally, or jhc's core or > grin representation, things get a bit more tricky. > > Although many core languages are somewhat similar, based on a typed > lambda calculus of some sort, the details will differ, and translating > between them can be lossy. > > For instance, looking at jhc core: > http://repetae.net/computer/jhc/manual.html#jhc-core-type-system > you can see it has a very rich language for dealing with strictness and > boxedness. For instances, a boxed value known to be in WHNF actually has a > different _type_ than one that is possibly unevaluated. Such > distinctions are quite useful for jhc's back end but not so much for > ghc's, hence ghc core doesn't make that distinction and any translation > between the two would 'lose' that useful information. > > In other cases things are even worse, for instance ghc has a powerful > type equality concept in its core language which jhc has no counterpart > for, so that information will be lost on translation. But losing that > information will actually cause the core to not type check, since ghc > core can type some things jhc core cannot (and vice versa) so coercions > or other mechanisms to bypass the type system will have to be > introduced. > > So, it is certainly possible to translate between the two, in fact, I > made a jhc core -> ghc core translator, but the code it produced was > necessarily riddled with unsafeCoerce#'s for everywhere the type systems > didn't quite match up. > > John > > > -- > John Meacham - ⑆repetae.net⑆john⑈ > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe >
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