[Boost-users] Using BOOST_STRING_TRIM_HPP to check whether trim_copy() is available?

Hi, I've got a header that I'd like to use in both application that use Boost and in ones that don't. Is there a define I can use to check whether Boost is available? In particular, I wish to use boost::trim_copy, but I don't want to force all files that include my header to use Boost. Olaf