Peter Alexander: > If I give some const object to a function: > > void render(const GameObject&); > > GameObject obj; > render(obj); > > I can be sure that my object will come back unmodified.
render() is free to modify the objects contained inside GameObject, because that const isn't transitive. > Yes, GameObject could be unreasonably mutilated by careless use of > mutable, but in practice that simply doesn't happen. Likewise, in Python there is no const attribute, yet those program often don't have bugs. The D transitive immutability is more rigid than the C++ const, it has a higher usage cost for the programmer, but it gives you back a stronger enforced semantics of immutability (strong enough for functional parallelism). Bye, bearophile
