> without operator overloading, it wouldn't be possible to implement lazy evaluation
I don’t understand that. You can have functions that return promises that then can get passed to other functions returning promises, and leave it either to the compiler or to an expression evaluator you write (that ideally runs at compilation time as much as possible) to optimize away anything not needed. For example (pseudo-code)
vector3D a = …
vector3D b = …
promise<vector3D> c = addLazily(a,b)
print c.x
in the end, could do the equivalent of
print a.x + b.x
I think you could make a modern C++ compiler do that for this simple example.
