[Haskell-cafe] Anonymous FFI calls

[Simon Peyton Jones]

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/1d982ba10f590828b78eba992e73315dee33f78a/
| 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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