On Sunday 29 November 2009 12:38:40 John Bytheway wrote:
I've used the compile-time log2 to determine the smallest integer type in which I can store any value of an enumeration. It's not easy to use, though; I'd prefer something that returned ceil(log2(n)) rather than floor(log2(n)). I can't make any sense of the existing example.
Here's what I use (if it can go into boost, that'd be one less thing I'd have to maintain): template <boost::static_log2_argument_type num> struct static_log2_ceil { BOOST_STATIC_CONSTANT( boost::static_log2_result_type, value = static_log2<num-1>::value+1 ); }; // Handle the case of static_log2 not allowing 0 template <> struct static_log2_ceil<1> { BOOST_STATIC_CONSTANT( boost::static_log2_result_type, value = 0 ); }; // Asking for log2(0) is an error template <> struct static_log2_ceil<0> {}; If this is useful to you, could you please create a trac ticket and attach the implementation as a patch? Regards, Ravi