Felipe Magno de Almeida wrote:
We had a similar discussion already. This involves some kind of re-evaluation of some of the input sequence after changing the internal state of the preprocessor. Wave currently does not support this.
Is it hard to make wave support this? I was thinking that with some guarantees from wave, wrt side-effects in the context, it could be really useful. The guarantees that I think would be needed are rollback-semantics in face of exceptions and no side-effects *before* callbacks are called. This would allow for backup of the context only if needed. Depending on how much work would be necessary I could work on it too for my SoC proposal, since it would easy a lot my work on the features I would implement.
In fact, it was easy to implement for this particular case. The 'evaluated_conditional_expression()' preprocessing hook now has a bool return value, which forces Wave to re-evaluate the expression as long as it is 'true'. The new prototype will be: template <typename ContextT, typename ContainerT> bool evaluated_conditional_expression(ContextT const &ctx, ContainerT const& expression, bool expression_value) { return false; } // ok to continue, do not re-evaluate expression Wave guarantees to keep the own state unchanged during this, which means you can save the context state, change a macro definition and return true to force the expression to be re-evaluated. This scheme should ensure a consistent behaviour. I'll check these changes into the CVS as soon as it will be up again. It won't be part of the Boost 1.34.0 release, though. Regards Hartmut
[snipped]
Thanks, -- Felipe Magno de Almeida _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost