Re: [boost] Re: quaternion/octonion compiler errors

From: Reece Dunn (msclrhd_at_[hidden])
Date: 2003-05-27 06:22:27

Marcelo E. Magallon wrote:

>  I'm baffled.  The compiler says:

>/usr/include/boost/math/quaternion.hpp: In function 
>`boost::math::quaternion<T>
>    boost::math::detail::quaternion_type_converter(const
>    boost::math::quaternion<U>&) [with T = float, U = double]':
>/usr/include/boost/math/quaternion.hpp:866:   instantiated from here
>/usr/include/boost/math/quaternion.hpp:449: error: `R_component_1' 
>undeclared
>    (first use this function)

I got the same sort of messages. It is even harder when GCC says:
   parse error before ';'!!!!

At least MS and Borland give better messages in this respect, e.g. missing 
parenthesis.

>  Looking at the preprocessor output, this is the problem code:

>/usr/include/boost/math/quaternion.hpp:866:

>     explicit quaternion(quaternion<double> const & a_recopier)
>     {
>->      *this = detail::quaternion_type_converter<float, 
>double>(a_recopier);

So the
/usr/include/boost/math/quaternion.hpp:449: error: `R_component_1' 
undeclared
    (first use this function)
error is related to the call to detail::quaternion_type_converter, that 
makes use of R_component_1().

>     }

>  Notice this is a specialization.  detail::quaternion_type_converter is
>  defined as:

You are referring to quaternion< float > and quaternion< double >.

>     namespace detail
>     {
>         template< typename T,
>                     typename U
>                 >
>         quaternion<T> quaternion_type_converter(quaternion<U> const & rhs)
>         {
>             return(quaternion<T>( static_cast<T>(rhs.R_component_1()),
>                                     static_cast<T>(rhs.R_component_2()),
>                                     static_cast<T>(rhs.R_component_3()),
>                                     static_cast<T>(rhs.R_component_4())));
>         };
>     }

>  The following code appears _before_ in the file:
>
>namespace boost{ namespace math
>{
>    template<typename T>
>    class quaternion
>    {
>       [...]
>       T R_component_1() const { return(a); }
>    };
>}}

>  The specialization for float and double appears _after_ the problem
>  code.

>  I have double checked that G++ 3.2 does compile the code.  Regression
>  in 3.3?

>  Hints?

I think I understand why G++ 3.3 is getting confused. The constructors 
appear near the top of the class definition, for example quaternion< float 
 >. The G++ compiler is strict about template checking, so will complain if 
something is wrong. I think they changed the preprocessor code, so that G++ 
3.3 won't find the member accessors because they are generated *after* the 
constructors, if you get me.

Try placing the constructor definitions at the end of the quaternion< float 
 > and quaternion< double > declerations.

Regards,
Reece

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