[boost] The perfect tutorial example?

I'm trying to come up with an example function to use in the tutorial for the parameters library. The function would ideally: * have four or fewer parameters, most of which have defaults. * have at least one defaulted parameter whose type would normally be a deduced function template parameter (when the argument is passed explicitly) * have a parameter whose default depends on the value of another parameter * have at least one parameter whose default value is of nontrivial complexity to compute (so I can demonstrate lazy defaults). * be realistic Any ideas would be most welcome. Thanks, -- Dave Abrahams Boost Consulting www.boost-consulting.com