NFD

std::future implies multi-threading.
What I desire is a mechanism to bundle success and failure callbacks.

After some thinking, it becomes clear that a jQuery-like future abstraction is not feasible in C++.

If Deferred::resolve is invoked before Deferred::done, the handler passed to Deferred::done should be invoked with the argument passed to Deferred::resolve. This implies that the argument should be stored in Deferred.

• store as a reference: the caller of Deferred::resolve may go away when Deferred::done is invoked.
• store as a pointer to a heap allocated object: it's unclear who should delete this object.
• store as a shared_ptr: complexity on caller of Deferred::resolve to create shared_ptr
• store a copy: cost of copying; many types are noncopyable