Re: "Semi-const" methods?

[Mafi]

Am 13.03.2011 23:27, schrieb Magnus Lie Hetland:

I have a data structure that's generally static (const, or even
immutable), but it has some utility storage, which caches certain
results during use. This caching etc. doesn't really affect the
semantics of the main object, and are reset between operations, so I
think it still would be useful to declare (and statically check) that
certain methods don't modify any of the *rest* of the structure (i.e.,
the "main parts").

I *could* declare the methods const, and pass in a second object (a
non-const parameter) for the caching etc. Or I cast the relevant parts
to const (assigning them to local variables) early on in the relevant
methods (dropping the const modifier on the method itself -- sort of a
bummer).

Any other ideas on how to handle this sort of "mostly const" or "const
where it counts" stuff? Perhaps my design intentions here are off to
begin with?-)

I found away which doesn't use casts or bugs.
Just use delegates/closures.

class C {
        int i;
        int delegate(int) getCache;

        this(int fi) {
                this.i = fi;    
        int lastX, lastR;
                this.getCache = (int x) {
                        if(x == lastX) return lastR;
            lastX = x;
            lastR = x * i;
            return lastR;
                };
        }

    const multiply(int x) {
        return getCache(x);
    }
}