(1) bitset(); (until C++11) constexpr bitset(); (since C++11) (2) bitset( unsigned long val ); (until C++11) constexpr bitset( unsigned long long val ); (since C++11) (3) template< class CharT, class Traits, class Alloc >
explicit bitset( const std::basic_string<CharT,Traits,Alloc>& str,
typename std::basic_string<CharT,Traits,Alloc>::size_type pos = 0,
typename std::basic_string<CharT,Traits,Alloc>::size_t