How to use dynamic bitset as member data of class?

Hello again, I enjoy to use the dynamic_bitset for the 1 bit correlation of radio interferometor. Very useful. But how to use the dynamic bitsets as the member data of the class? class multi_bitsets{ const boost::dynamic_bitset<> db1(20,1ul); const boost::dynamic_bitset<> db2(20,1ul); this kind of code always gives me the following errors: $ g++ multi_bitset_test00.cpp multi_bitset_test00.cpp:19: error: expected identifier before numeric constant multi_bitset_test00.cpp:19: error: expected `,' or `...' before numeric constant multi_bitset_test00.cpp:19: error: ISO C++ forbids declaration of `parameter' with no type Please let me know how to use the dynamic bitsets as the member data of the class, thank you. fuji