Sharing: member type deduction for member pointers (Alf's device?)

[Vladimir Jovic]

Alf P. Steinbach /Usenet wrote:

> #include <progrock/cppy/PyClass.h>      // PyWeakPtr, PyPtr, PyModule, 
> PyClass
> using namespace progrock;
> 
> namespace {
>     using namespace cppy;
> 
>     struct Noddy
>     {
>         PyPtr       first;
>         PyPtr       last;
>         int         number;
> 
>         Noddy( PyWeakPtr pySelf, PyPtr args, PyPtr kwArgs )
>             : number( 0 )
>         {
>             devsupport::suppressUnusedWarning( pySelf );
> 
>             PyWeakPtr   pFirstName  = 0;
>             PyWeakPtr   pLastName   = 0;
> 
>             static char*    kwlist[] = { "first", "last", "number", 0 };
> 
>             ::PyArg_ParseTupleAndKeywords(
>                 args.rawPtr(), kwArgs.rawPtr(), "|OOi", kwlist,
>                 pointerTo( pFirstName ), pointerTo( pLastName ), &number
>                 )
>                 >> Accept< IsNonZero >()
>                 || throwX( "Invalid args" );
> 
>             if( pFirstName != 0 )   { first = pFirstName; }
>             if( pLastName != 0 )    { last = pLastName; }

Why not initiallize all member variables in the initializer list?


>         }
> 
>         PyPtr name()
>         {
>             (first != 0)
>                 || throwX( ::PyExc_AttributeError, "first" );
>             (last != 0)
>                 || throwX( ::PyExc_AttributeError, "last" );

Nice trick. I would still find this more readable :

if ( first != 0 )
{
   throwX( ::PyExc_AttributeError, "first" );
}


>             return (PyString( first ) + L" " + PyString( last )).pyPtr();
>         }
>     };
> 
>     struct NoddyPyClass: PyClass< Noddy >
>     {
>         NoddyPyClass( PyModule& m, PyString const& name, PyString const& 
> doc )
>             : PyClass< Noddy >( m, name, doc, Exposition()
>                 .method(
>                     L"name",    CPPY_GLUE( name ),
>                     L"Return the name, combining the first and last name"
>                     )
>                 .attribute(
>                     L"first",   CPPY_GLUE( first ),     L"first name"
>                     )
>                 .attribute(
>                     L"last",    CPPY_GLUE( last ),      L"last name"
>                     )
>                 .attribute(
>                     L"number",  CPPY_GLUE( number ),    L"noddy number"
>                     )
>                 )
>         {}
>     };
> 
>     class NoddyModule: public PyModule
>     {
>     private:
>         NoddyPyClass    noddyPyClass_;
> 
>     public:
>         NoddyModule()
>             : PyModule(
>                 L"noddy2", L"Example module that creates an extension 
> type." )
>             , noddyPyClass_( *this,
>                 L"Noddy", L"A Noddy object has a name and a noddy number" )


hmmm what is L ?