Question

I extended a const function, and everytime that const function is called I have to create a map. As in

int foo() const {
  map<int, int> bar;
  // setup bar
  ...

  return utility::eval(bar);
}

But declaring bar is very expensive. I can cut my CPU footprint in half by declaring bar is an instance variable, but doing so doesn’t respect constess. Is there a non-hacky way to get the best of both worlds?

Answer 1

Yes.

class Foo {
    mutable map<int, int> bar;
    ...
}

See also http://www.highprogrammer.com/alan/rants/mutable.html and triple check whether it makes sense for you to actually use mutable here.