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From: Marcelo E. Magallon (mmagallo_at_[hidden])
Date: 2003-05-27 07:57:22

On Tue, May 27, 2003 at 12:22:27PM +0100, Reece Dunn wrote:

> > I'm baffled. The compiler says:
> [...]
> I got the same sort of messages. It is even harder when GCC says:
> parse error before ';'!!!!

 Heh. I meant I was baffled by the problem at large, not by the
 compiler message. 3.x is so much better in this respect! At least the
 messages are readable now :-) (scary nightmares about those 1000+ lines
 long messages because of a misplaced semicolon)

 Anyway, I got it. Context diff against CVS attached.

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

 Yes, that sent me in the right direction, even if I still don't
 understand what exactly is going on. At that point in the code the
 compiler knows:

    1. There's a template quaternion<T>
    2. There's a method T quaternion<T>::R_component_1()
    3. There's a forward declaration for a quaternion<float> and a
       quaternion<double> specialization.
    4. There's a function template for quaternion_type_converter<T,U>
    5. Said function calls R_component_1()
    6. Said function is instantiated for T=float, U=double.
    7. At this point the compiler complains that:

        float quaternion<float>::R_component_1()

       is not defined. The compiler is right I guess, there's no
       definition for that function, only a declaration (see 3.)

 The patch makes a declaration for the function in 4. and pushes its
 definition to the end of the file. That makes the compiler happy. I
 don't think this will affect other compilers.


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