At this point I am not familiar with MPL, so my apologies if my suggestion is naive... You use template recursion to support an arbitrary number of dimensions at compile-time, which is fine. The natural means of handling the base case of N=1 is (as I see it) a partial specialization of the MyArray class. Something like this: #include <vector> template < class T, int N > class MyArray { public: MyArray<T, N-1> operator[]( unsigned int n ) { return m_arr[ n ]; } private: std::vector< MyArray< T, N - 1 > > m_arr; }; template < class T > class MyArray<T,1> { public: T operator[]( unsigned int n ) { return m_arr[ n ]; } private: std::vector< T > m_arr; }; void foo() { MyArray< int, 2 > twodim; // populate twodim with values... int val = twodim[ 2 ][ 1 ]; } Hope this helps... - Rod On 11/16/05, Manfred Doudar <manfred.doudar@metoceanengineers.com> wrote:

Martin Bonner wrote:

...

...

Manfred Doudar wrote:

...

/* Now, how do I get T out when Rank == 1, ... compiler complains about seeing a MyArray/blitz::Array of <T, Rank = 0> (, which is not defined for blitz Arrays) */ template <typename T, int Rank> typename boost::mpl::if_ < typename boost::mpl::equal_to < boost::mpl::int_<Rank> , boost::mpl::int_<1> >::type , T , blitz::Array<T,

boost::mpl::int_<Rank>::prior::value>

^ Oops typo, should be: MyArray<T,

boost::mpl::int_<Rank>::prior::value>

... but nonetheless, the problem remains ...

...

>::type MyArray<T, Rank> :: operator[] (const int& index) throw(); { // Slicing

How about a helper traits class?

template <typename T, int Rank> struct SliceType { typedef typename MyArray<T, Rank-1> type; };

template <typename T> struct SliceType<T,1> { typedef T type; };

template <typename T, int Rank> typename SliceType<T,Rank>::type MyArray<T,Rank> :: operator[] (const int& index) throw();

Now I'm sure that ought to have worked (even after modifying as you've suggested) ... but the problem _still persists_ , not per say on the definition of return type, but seemingly inside the _template body_, where the *static_cast* is done to map the final result accordingly ... please see below:

Partial Code Listing: --------------------

template <typename T, int Rank> typename SliceType<T, boost::mpl::int_<Rank>::value>::type MyArray<T, Rank> :: operator[] (const int& index) throw() { // Slicing

blitz::TinyVector<boost::variant<blitz::Range, blitz::nilArraySection>, 2> plist; this->getParamList(plist);

return

// *********************************************** // ** Complier complains about this cast seeing // ** MyArray/blitz::Array <T, 0> // ** when Rank == 1 // ** ... see partial compiler error msg below // *********************************************** static_cast< typename SliceType<T, // ** [ Line 697 ] ** boost::mpl::int_<Rank>::value>::type > (

((* static_cast<const blitz::Array<T, boost::mpl::int_<Rank>::value> *> (this))

/* the parameter list */ (index, *boost::get< typename boost::mpl::if_< typename boost::mpl::less< boost::mpl::int_<1> , boost::mpl::int_<Rank> >::type , blitz::Range , blitz::nilArraySection >::type >

(&plist(boost::mpl::if_< typename boost::mpl::less< boost::mpl::int_<1> , boost::mpl::int_<Rank> >::type , boost::mpl::int_<0> , boost::mpl::int_<1> >::type::value ) )

/* , ... we can extend the parameter list with Boost.PP */ );

}

(Partial) Compiler Error Message: ---------------------------------

In member function `SliceType<T, boost::mpl::int_<Rank>::value>::type MyArray<T, Rank>::operator[](const S&) [with S = int, T = float, int Rank = 1]': arr.cc:197: instantiated from here arr.cc:697: invalid static_cast from type `blitz::Array<float, 0>' to type ` float'

<snip .. more messages>

/usr/local/include/blitz/array/storage.h:60: no match for call to `( blitz::TinyVector<int, 0>) (int&)'

<snip .. more messages>

Somewhere in main(..) ---------------------

blitz::Array<float, 2> b2(2, 2); // 2D array (2 x 2)

b2 = 1.1, -2.2, -9.9, 8.8;

MyArray<float, 2> a2(b2);

std::cout << a2[1] ; // this works std::cout << a2[1][1] ; // ** [Line 197] ** the problem is here

Any and All help is Appreciated, I know it's got to be something simple, I just can't see it yet.

With Thanks, -- Manfred Doudar MetOcean Engineers www.metoceanengineers.com

_______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost

-- Rod Philander rodrigo.philander@gmail.com

Manfred Doudar wrote:

Martin Bonner wrote:

...

...

Manfred Doudar wrote:

...

/* Now, how do I get T out when Rank == 1, ... compiler complains about seeing a MyArray/blitz::Array of <T, Rank = 0> (, which is not defined for blitz Arrays) */ template <typename T, int Rank> typename boost::mpl::if_ < typename boost::mpl::equal_to < boost::mpl::int_<Rank> , boost::mpl::int_<1> >::type , T , blitz::Array<T,

boost::mpl::int_<Rank>::prior::value>

^ Oops typo, should be: MyArray<T,

boost::mpl::int_<Rank>::prior::value>

... but nonetheless, the problem remains ...

...

>::type MyArray<T, Rank> :: operator[] (const int& index) throw(); { // Slicing

How about a helper traits class?

template <typename T, int Rank> struct SliceType { typedef typename MyArray<T, Rank-1> type; };

template <typename T> struct SliceType<T,1> { typedef T type; };

template <typename T, int Rank> typename SliceType<T,Rank>::type MyArray<T,Rank> :: operator[] (const int& index) throw();

With a great deal of thanks to Martin, and a few hours sleep, I've got the thing working. ... Sorry for the noise everyone, and in future I'll try not to post anything unless I've been otherwise well rested. Cheers, -- Manfred Doudar MetOcean Engineers www.metoceanengineers.com