Re: [Boost-users] [Fusion, maybe?] Workings of ADL.

9 Sep 2010


      AMDG

Robert Jones wrote:
...
On Wed, Sep 8, 2010 at 5:57 PM, Steven Watanabe wrote:
...
14.8.1/6:
"... But when a function template with explicit template arguments
is used, the call does not have the correct syntactic form unless
there is a function template with that name visible at the point of
the call...."
That is just the oddest rule! Going back to my original example, I could
make it work just by adding an arbritary declaration of at_c(),
#include 
#include 
typedef boost::fusion::vector V;
template  void at_c( const U & );
int first( const V & v )
{
    return at_c<0>( v );
}
which doesn't even need to be defined anywhere. If such a namespace-enabling
template were to be removed, thus breaking the look-up used in my 'first()'
function
it would be a horrible bug to find!
I think the rationale is that the the compiler needs to
know that at_c is a template in order to parse the
expression.  It's basically the same reason we need
to use template and typename to disambiguage.

In Christ,
Steven Watanabe