*** HDirect Hugs support problem ***

[Dominic Verity]

In the past week or so I've been playing with HDirect to interface Hugs with some statistical packages and have encountered a problem with HDirects support for reference arguments of type double* or float*.   Specifically I have a function with prototype   void cumnor( double* arg, double* result, double* ccum);   which I wanted to interface to hugs/GHC using the following IDL specification:   > stub_include("cdflib.h") > module Cdlib { > > [pure]void cumnor >   ( [in]double* arg, >     [out]double* result, >     [out]double* ccum ); >    > };   giving a function cumnor :: Double -> (Double, Double) in Haskell. When compiled using IHC this worked fine for GHC-4.03, however it returned gobbledegook in Hugs.   In the end I've tracked this down to a problem in the construction of the support DLL AddrBits.dll as supplied in the Win32 precompiled version of HaskellDirect 0.15.   To fix the problem, I needed to supply the obvious header file for AddrBitsPrim.c and include it in the AddrBits.idl file by adding   > stub_include("AddrBitsPrim.h")   to the start of that file.   Now I recompiled using the makefile default compiler flags to generate AddrBits.c from AddrBits.idl and compile both AddrBits.c and AddrBitsPrim.c to object code. Finally I linked this all into a DLL using:   > dllwrap -mno-cygwin --target=i386-mingw32 --def HugsMod.def AddrBits.dll_o AddrBitsPrim.dll_o -o AddrBits.dll   This new dll seems to have solved my problem completely.   Please note: It was not enough to simply recompile AddrBits.dll, the c compiler (egcs-2.91.66) definately requires the extra help the header file provided.   All the Very Best (and congratualtions on HDirect)   Dr. Dominic Verity Director Categorical Solutions Pty Ltd Uncertainty Management and Strategy.   Suite 405, 71 Archer Street, Chatswood, NSW 2067, Australia.   email: [EMAIL PROTECTED]   Visit our web site at: http://www.categoricalsolutions.com.au   "Viewpoints" is Categorical Solutions complimentary newsletter delivered to your desktop via email. You can subscribe to "Viewpoints" by clicking on the link below and entering your e-mail address in the Subscribe panel on the side bar. http://www.categoricalsolutions.com.au