HaskellDirect

What is it?

HaskellDirect is an IDL compiler for Haskell, which offers a helping hand to the Haskell programmer that wants to better interact with and reuse external code.

Interfacing Haskell code to external code involves the conversion of values between the Haskell world and the outside, as data representations and details of how memory is managed, are worlds apart at times. Manually writing the boilerplate code that takes care of this conversion is about as exciting as watching grass grow and, as a result, error prone.

Using an Interface Definition Language (IDL) as basis, HaskellDirect automates the generation of such impedance matching code, generating all the necessary marshaling code for you.

With IDL, the functionality provided by a programming interface is specified in a programming language neutral framework. The HaskellDirect IDL compiler converts this specification into a set of method stubs. Depending on how the compiler is invoked, these stubs can be used to:

• Call upon external functions from within Haskell,
      HaskellDirect creates bindings to external (C-callable) libraries.
• Let external code call upon Haskell functions,
      HaskellDirect creates foreign/external language interfaces to Haskell libraries.
  
• Call COM (Microsoft's Component Object Model) methods from Haskell,
      HaskellDirect helps you use Microsoft COM components from within Haskell.
      The generated stubs can be used with Hugs98 or GHC.
• Create COM method wrappers,
      HaskellDirect packages up Haskell code as COM components.
  

The HaskellDirect IDL compiler currently groks both the OSF DCE dialect of IDL (including the various extensions introduced by the Microsoft IDL compiler) and the OMG IIOP/CORBA dialect. (Only the former can be used for describing COM interfaces.)

Documentation

• HaskellDirect user's manual[last updated: 4th November 1999.]
    Sigbjorn Finne
  User documentation, which includes a number of worked IDL
  examples together with pointers to other IDL on-line resources.
  The manual is also available in more printable formats:
  [ a4 (PS) | letter (PS) ]

• Calling Hell From Heaven And Heaven From Hell.
    Sigbjorn Finne, Daan Leijen, Erik Meijer and Simon Peyton Jones
  
  Paper which shows how to wrap up Haskell code as COM components.
  (presented at ICFP'99.)
• H/Direct: A Binary Foreign Language Interface for Haskell
    Sigbjorn Finne, Daan Leijen, Erik Meijer and Simon Peyton Jones
  
  Paper which presents, in a relatively formal and precise manner,
  the definition of the mapping between Haskell and IDL.
  (presented at ICFP'98.)
• Design document [last updated: 6 July 98 - now a bit dated in places.]
    Sigbjorn Finne
  Document which introduces HaskellDirect's various features and
  how they're supported, including a Haskell COM component design.
  Also available in more printable forms:
      [ PostScript ( a4 / letter ) | Dvi ( a4 / letter ) ]

• A foreign function interface for Haskell [version 0.99, last updated: 02 May 2000]

  Sigbjorn Finne
Document specifying the foreign function interface used by nhc98, STG/Hugs and GHC.
Also available in more printable forms:
    [ PostScript ( a4 / letter ) | Dvi ( a4 / letter ) ]

Download

• 0.21:

The current version of HaskellDirect is 0.21 (released Jan 2004), and is only available in source format:



• Source dist

The sources compiles out of the box with recent versions of GHC, such as ghc-6.2. The IDL compiler's output can be used together with both GHC and Hugs98.

HDirect comes with a BSD-style license, and the sources are also available via the GHC/fptools CVS server (in fptools/hdirect.) Compared to 0.16, 0.17 fixes a slew of minor bugs/problems; the feature set is unchanged.

• 0.16:

[Note: Mostly of historical interest; 0.16 doesn't work with current versions of GHC nor Hugs]
The last major release was 0.16 (released 04/11/99), which is available in source and binary format:


• Source dist
• Win32 installer[ http | ftp ]

If you want to compile up the 0.16 sources, you'll need ghc-4.04 / 4.05. The 0.16 Win32 binary distribution can be used to produced output for use with ghc-4.04/4.05 and Hugs98.

• CVS:

The HaskellDirect sources are available via the Haskell CVS, as module fptools/hdirect.

Feedback/reporting bugs

Please direct any feedback or bug reports to sof at galois.com