Re: [Boost-users] Can not compile a program that uses typeof package by gcc?

21 Oct 2008

      AMDG

Peng Yu wrote:
...
...
In line 51-55 of you attached file, it says the following.
template 
 Y::result_type>
   operator*(const Y<T1> &y, const T2 &t) {
     return Y<T1>(y.the_t() * t);
   }
This way requires that I have to explicitly say 'multiply_traits' is
from the namespace A. I wanted to use the following instead, which
does not need to specify which the namespaces T1 and T2 are. But the
following code still results in the compiler error.
template 
 Y
   operator*(const Y<T1> &y, const T2 &t) {
     return Y<T1>(y.the_t() * t);
   }
My question is not resolved. I'm attaching the source file with some
comments to avoid any confusion. Would you please take another look at
the problem?
Alright.  If you don't want to refer to multiply_traits from namespace
A, then put a generic multiply_traits somewhere else.  When it is defined
using Boost.Typeof, it will work for any types.  It does not matter what
namespace multiply_traits is defined in.  Really.

template
struct typeof_multiply {
    BOOST_TYPEOF_NESTED_TYPEDEF_TPL(nested, (make<T1>() * make<T2>()));
    typedef typename nested::type type;
};

...

template
Y::type> operator*(...);

Really, all this does is to move the typeof calculation into a separate
metafunction.

In Christ,
Steven Watanabe