On 04/21/2010 07:16 PM, Christian Holmquist wrote:
Hi,
IIUC, c+0x allows the safe bool idiom to be implemented as
explicit operator bool() const { ...}
but in c+03 emulating that behaviour is a bit messy.
There appears to be a solution for c+03 in boost/smart_ptr/detail/operator_bool.hpp, but it's targeted for the smart_ptr classes only.
Would it be possible to extract operator_bool.hpp into a reusable macro, something like:
#include<boost/utility/operator_bool.hpp> struct some { BOOST_EXPLICIT_OPERATOR_BOOL( m_value != 0; )
int m_value; };
What do you think?
I think such a tool would be useful. But I found it more convenient to express explicit operator bool through operator!. This allows the check to be arbitrarily complex, and the approach adds to compatibility with some compilers. See here: <http://boost-log.svn.sourceforge.net/viewvc/boost-log/trunk/boost-log/boost/log/detail/unspecified_bool.hpp?revision=432&view=markup> Usage example: struct some { BOOST_LOG_OPERATOR_UNSPECIFIED_BOOL() bool operator! () const { return m_value == 0; } int m_value; };