On Tue, 9 Mar 2004 11:30:15 -0500 Douglas Gregor <gregod@cs.rpi.edu> wrote:
I also need an efficient way for accessing slots randomly. For instance some of the Win32 listbox messages have item indexes. I'd like to implement each item as a slot, but I need a way to access the slots based on the item index, so I could call just the right slot. listboxes can contain a lot of items so propagating the messages to all items is not an option.
That'd be a much bigger change to Signals. For one, we'd be breaking the logarithmic complexity of inserting a new element in a particular group.
If I understand the original statement, I have a similar requirement, and have done it by implementing an addition class, I call multisignal (after multimap, multiset, and so forth). It basically holds an addition to the tuple library that I call dynamic_tuple, which provides direct access to any type, while preserving type safety both at run time and compile time. You can use a type as an index into a dynamic_tuple, and still get constant time lookup. This forms a basis for the multisignal, which provides a wrapper around Boost.Signal to allow multiple signals to be raised, using the same signal object. The algorithmic complexity can be minimized to constant time lookup of the signal object using another libary I call type_to_index, which provides a special zero-based index for a specific type, relative to the collection in which the type is used as an index. Sounds complicated, but it is quite simple. However, to get the type_to_index, you have to create explicit template instantiations, or allow static data members (which some are opposed to, depending on OS preference).