On 11.04.2011, at 20:15, Matt Calabrese wrote:
However, in C++0x, there is a new way to use enable_if by altering neither the function parameter list nor the specification of the return type. It can be used with operators, constructors, variadic function templates, and even overloaded conversion operations (the latter of which was previously considered impossible). The way to do it is with C++0x default function template parameters.
That's really nice, but I think the syntax might be improved. How about adding a ::value to enable_if (and the other templates) to allow your example to look like this: template< class... T, bool = boost::enable_if_c< sizeof...( T ) == 10 >::value > test( T&&... ); template< class T, bool = boost::enable_if< boost::is_arithmetic< T > >::value > operator T() const; etc.? Get rid of typename, *&, boost::enabler and if you like, you can write 'bool Enabled = ...' instead of 'bool = ...' to be more verbose in your code. Of course, ::value is non-existent if the condition of enable_if is not met, it is not false. I made a quick test with gcc 4.6.0 and it seems to work fine. Plus it allows extending the existing enable_if without breaking anything (AFAICS). Regards, Daniel