You can mark member variables "mutable" to mean they aren't const when the class is. This is generally used for caches and stuff like that. In general, declaring a method const is used to imply logical constness instead of physical constness. That is, it means that doing it 2x with the same arguments should give the same answer, rather than that none of the bits should change.
Let me consult with the high IMP society about some IMP scoring and caching design issues, don't wanna mess things up.
I've been profiling code, and consequently wanted to cache some intermediate computations that are made during pair score evaluations (e.g., the distance between particles). I just need the last intermediate from each computation, so I thought of simply adding a [cache_] variable to my scoring class, and store the intermediate computations there. BUT, ::evaluate() and ::evaluate_index() are const functions, so I can't do that. Another option is to add an output parameter to ::evaluate(), but that's also not very clean. Is it absolutely necessary that these functions are const? Or any other suggestions so that I can cache intermediate calculations during ::evaluate()? This can speed some things up considerably.
Barak