[Haskell-cafe] Anonymous FFI calls

[Francesco Mazzoli]

Thanks to everyone who replied!

It seems like that through a combination of facilities like `libffi'
and `addTopDecls' I can do everything that I wanted to do.

I still want to take a shot at implementing anonymous FFI calls, since
IMHO I think they are a very small but useful addition to the
language.

Francesco

On 12 February 2015 at 09:29, Simon Peyton Jones <simonpj at microsoft.com> wrote:
> |  Also, I meant to say that addTopDecls is only exported by
> |  "Language.Haskell.TH.Syntax".  While this is a digression, there are a
> |  few other handy functions that are oddly left out of
> |  "Language.Haskell.TH": addDependentFile, addModFinalizer, and possibly
> |  more.
>
> That does seem wrong.  Do make a patch!
>
> SIMon
>
> |
> |  -Michael
> |
> |  On Wed, Feb 11, 2015 at 3:25 PM, Simon Peyton Jones
> |  <simonpj at microsoft.com> wrote:
> |  > I would LOVE someone to improve the documentation for addTopDecls.
> |  Manuel Chakravarty and Geoff Mainland were responsible for the
> |  implementation.
> |  >
> |  > Simon
> |  >
> |  > | -----Original Message-----
> |  > | From: ghc-devs [mailto:ghc-devs-bounces at haskell.org] On Behalf Of
> |  > | Michael Sloan
> |  > | Sent: 11 February 2015 23:19
> |  > | To: Francesco Mazzoli
> |  > | Cc: ghc-devs at haskell.org; haskell
> |  > | Subject: Re: [Haskell-cafe] Anonymous FFI calls
> |  > |
> |  > | It seems like addTopDecls[1] will able to help here.
> |  Unfortunately,
> |  > | the function is not well documented and not very discoverable
> |  > | because it's only exported by Language.Haskell.TH.
> |  > |
> |  > | The documentation doesn't mention that it can only be used to
> |  create
> |  > | new top level functions and FFI imports[2].  I think that adding
> |  FFI
> |  > | imports was the main motivation for implementing it.   In the past
> |  > | I've wanted to generate instances via this function, but
> |  > | unfortunately it's not implemented..
> |  > |
> |  > | Hope that helps!
> |  > | -Michael
> |  > |
> |  > | [1] http://hackage.haskell.org/package/template-haskell-
> |  > | 2.9.0.0/docs/Language-Haskell-TH-Syntax.html#v:addTopDecls
> |  > |
> |  > | [2]
> |  > |
> |  https://github.com/ghc/ghc/blob/1d982ba10f590828b78eba992e73315dee33
> |  > | f78a/
> |  > | compiler/typecheck/TcSplice.hs#L818
> |  > |
> |  > | On Wed, Feb 11, 2015 at 2:26 AM, Francesco Mazzoli <f at mazzo.li>
> |  wrote:
> |  > | > Hi,
> |  > | >
> |  > | > I am in a situation where it would be very useful to call C
> |  > | > functions without an explicit FFI import.  For example, I'd like
> |  > | > to be able to do
> |  > | >
> |  > | >     (foreign import ccall "cadd" :: CInt -> CInt -> CInt) 1 2
> |  > | >
> |  > | > instead of declaring the foreign import explicitely at the top
> |  level.
> |  > | >
> |  > | > Is there a way to do this or to achieve similar results in some
> |  > | > other way?
> |  > | >
> |  > | > If not, I imagine it would be easy to implement such a facility
> |  in
> |  > | > GHC, given that the code implementing calling to C functions
> |  must
> |  > | > already be present to implement "proper" FFI imports.  I think
> |  > | > such an addition would be useful in many cases.
> |  > | >
> |  > | > Thanks,
> |  > | > Francesco
> |  > | > _______________________________________________
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