Re: [Haskell-iPhone] FFI for living in C

Getting the TH/Objective Haskell layer going will be GLORIOUS if it can achieve easier integration On Dec 1, 2012, at 6:43 PM, Luke Iannini wrote:

Hi guys,

It's also possible to start the Haskell runtime from within C/C++, using the hs_init() and hs_exit() functions (you can just call them each one at startup and shutdown before calling into any Haskell code that's been "foreign export"ed), to skip the c_main business.

See 8.2.1.1 here: http://www.haskell.org/ghc/docs/7.4.1/html/users_guide/ffi-ghc.html

There's a great chapter in Real World Haskell on exporting and importing functions to call to and from C/C++: http://book.realworldhaskell.org/read/interfacing-with-c-the-ffi.html

For Objective-C, Objective Haskell is an even higher level (and quite excellent) project for calling to and from Obj-C and converting its standard data types (NSDictionaries, NSStrings, NSData etc.) into Haskell's (Maps, Text, ByteStrings etc.), and vice-versa. https://github.com/jspahrsummers/ObjectiveHaskell

It uses Template Haskell to make importing and exporting extremely easy and clean, but sadly ghc-ios doesn't support TH quite yet. I have an experimental branch that replaces the TH with manually-written boilerplate but of course it's a lot messier. I'll be publishing it soon anyway : ).

Cheers Luke

On Sat, Dec 1, 2012 at 1:26 PM, Stephen Paul Weber wrote:

...

Somebody claiming to be Casey Basichis wrote:

...

Is the FFI the right tool for a situation where, while used extensively, Haskell is more or less there to take in data, like lists and spit out data like vectors etc back to C.

My current favourite way to do this is to start in Haskell-land and call some entry-point function in extern "C" that takes function pointers as arguments. These function pointers become the way that C++ code can call back into Haskell-land.

This is what I am using for http://github.com/singpolyma/haskades

-- Stephen Paul Weber, @singpolyma See http://singpolyma.net for how I prefer to be contacted edition right joseph

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