Boost signals also handles multiple (or zero) callbacks associated with a single signal. I'm not sure but I believe it also allows calling the slot at a later p

Boost signals also handles multiple (or zero) callbacks associated with a single signal. I'm not sure but I believe it also allows calling the slot at a later point from a message pump – certainly Qt's signals and slots do. A more direct analogue of the type discussed in the article is std::function, which is simply a type that can contain any one callable (function pointer or function object, including lambda functions) or can be empty (like a null function pointer), and can be called in an immediate synchronous way.