brary is still backward-compatible with
    the former one (so you're not <em>forced</em> change any existing code),
    but the old usage is deprecated. Though it was arguably simpler and more
    intuitive than using <a href="#chaining">base class chaining</a>, it has
    been discovered that the old practice of deriving from multiple operator
    templates can cause the resulting classes to be much larger than they
    should be. Most modern C++ compilers significantly bloat the size of
    classes deriv