I'm just looking through the variant library docs in detail and had the following commments: * http://www.boost.org/regression-logs/cs-win32_metacomm/doc/html/variant/tuto... shows static_visitor being used with no arguments and yet http://www.boost.org/regression-logs/cs-win32_metacomm/doc/html/boost/static... doesn't indicate any default for the first parameter. Also, once you start using an argument in the tutorial, it comes with no explanation, which is confusing. * It's not obvious why we're deriving anything from static_visitor. It seems as though it shouldn't be necessary and that it might not be simplifying anything. * I find the dual nature of apply_visitor confusing. With two arguments it is an imperative command: "apply this visitor." With one argument it is a wrapper generator or something like that: "make this visitor into a function object that operates on variant<T0,...TN> instead of on T0, ... TN directly." [Actually, I'm not sure the latter description is accurate and it wouldn't hurt to have it spelled out in the docs.] I think it would be better to use two names rather than overloading one name in these two very different ways. * I have a very clear mental model for what a non-recursive variant is doing, which gives me a clear of its costs and of where I'd use it: it's like a supercharged union. From reading your docs it's very hard to form the same kind of mental model for a recursive variant. It would help to be explicit about what the library generates for you in the recursive case. * The make_recursive_variant example is vague. It should describe what the result is equivalent to. I presume it's something like: variant<int, ... ...uhh, interesting: I don't think you can express that example in terms of just variant and recursive_wrapper. However, the text implies that make_recursive_variant is just a less-flexible way to achieve a subset of the same goals. * binary visitation: "Notably this feature requires that binary visitors are incompatible with the visitor objects discussed in the tutorial above, as they must operate on two arguments." I don't get it. I can make an object whose function call operator overload set can operate on both 1 and 2 arguments. * It seems like visitor_ptr is a very specialized name for something very general-purpose. Doesn't bind(fp) (or some other boost construct) do the same thing? -- Dave Abrahams Boost Consulting www.boost-consulting.com