How would one support a variant data type in modern (post f77) ?  I am
writing some OLE code today (in C++ though) and have run across the OLE
VARIANT data type:  http://docstore.mik.ua/orelly/perl3/perlnut/ch23_04.htm

I would either use equivalences or a structure / map / union / record.

Thanks,
Lynn

In article <i0beav$ps2$1@news.eternal-september.org>,
 Lynn McGuire <lmc@winsim.com> wrote:

> How would one support a variant data type in modern (post f77) ?  I am
> writing some OLE code today (in C++ though) and have run across the OLE
> VARIANT data type:  http://docstore.mik.ua/orelly/perl3/perlnut/ch23_04.htm
> 
> I would either use equivalences or a structure / map / union / record.

This is for passing some item to a routine in another language, right?  
I would probably pack/unpack the bits using either transfer() or 
internal I/O.

$.02 -Ron Shepard

"Ron Shepard" <ron-shepard@NOSPAM.comcast.net> wrote in message 
news:ron-shepard-EAE3DE.21043628062010@news60.forteinc.com...
> In article <i0beav$ps2$1@news.eternal-september.org>,
> Lynn McGuire <lmc@winsim.com> wrote:
>
>> How would one support a variant data type in modern (post f77) ?  I am
>> writing some OLE code today (in C++ though) and have run across the OLE
>> VARIANT data type: 
>> http://docstore.mik.ua/orelly/perl3/perlnut/ch23_04.htm
>>
>> I would either use equivalences or a structure / map / union / record.
>
> This is for passing some item to a routine in another language, right?
> I would probably pack/unpack the bits using either transfer() or
> internal I/O.
>
> $.02 -Ron Shepard

IIRC, DVF/CVF/IVF treat a variant as a derived type, but the innards are 
buried in supplied modules and libraries.

I've only done Office Automation from VBA, where it's easy. Yes, some people 
deride VB/VBA as junk. Whether its wretchedness under the hood is deserved, 
I don't know.

Elliot

> How would one support a variant data type in modern (post f77) ?  I am
> writing some OLE code today (in C++ though) and have run across the OLE
> VARIANT data type: http://docstore.mik.ua/orelly/perl3/perlnut/ch23_04.htm

Here is the C version from from oaidl.h:

typedef /* [wire_marshal] */ struct tagVARIANT VARIANT;

struct tagVARIANT
     {
     union
         {
         struct __tagVARIANT
             {
             VARTYPE vt;
             WORD wReserved1;
             WORD wReserved2;
             WORD wReserved3;
             union
                 {
                 LONGLONG llVal;
                 LONG lVal;
                 BYTE bVal;
                 SHORT iVal;
                 FLOAT fltVal;
                 DOUBLE dblVal;
                 VARIANT_BOOL boolVal;
                 _VARIANT_BOOL bool;
                 SCODE scode;
                 CY cyVal;
                 DATE date;
                 BSTR bstrVal;
                 IUnknown *punkVal;
                 IDispatch *pdispVal;
                 SAFEARRAY *parray;
                 BYTE *pbVal;
                 SHORT *piVal;
                 LONG *plVal;
                 LONGLONG *pllVal;
                 FLOAT *pfltVal;
                 DOUBLE *pdblVal;
                 VARIANT_BOOL *pboolVal;
                 _VARIANT_BOOL *pbool;
                 SCODE *pscode;
                 CY *pcyVal;
                 DATE *pdate;
                 BSTR *pbstrVal;
                 IUnknown **ppunkVal;
                 IDispatch **ppdispVal;
                 SAFEARRAY **pparray;
                 VARIANT *pvarVal;
                 PVOID byref;
                 CHAR cVal;
                 USHORT uiVal;
                 ULONG ulVal;
                 ULONGLONG ullVal;
                 INT intVal;
                 UINT uintVal;
                 DECIMAL *pdecVal;
                 CHAR *pcVal;
                 USHORT *puiVal;
                 ULONG *pulVal;
                 ULONGLONG *pullVal;
                 INT *pintVal;
                 UINT *puintVal;
                 struct __tagBRECORD
                     {
                     PVOID pvRecord;
                     IRecordInfo *pRecInfo;
                     } 	__VARIANT_NAME_4;
                 } 	__VARIANT_NAME_3;
             } 	__VARIANT_NAME_2;
         DECIMAL decVal;
         } 	__VARIANT_NAME_1;
     } ;


Whew!,
Lynn