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

21 Oct 2008

      On Mon, Oct 20, 2008 at 10:19 PM, Steven Watanabe  wrote:
...
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.
This is a reasonable solution. But no matter which namespace
multiply_traits puts, it pollutes that namespace. Since namespace is a
way to better organized the code, I'd rather multiply_traits be in the
same namespace as that of its associated types.

Since Koenig lookup can be used to deduce the namespace of a function
based on whether its arugments are from, I'm wondering why C++ does
not allow such look up for templates?  If Koenig lookup can be used
for template, then the problem is solved.

Thanks,
Peng