So I have some pretty extensive functional code where the main data type is immutable structs/classes. The way I have been declaring immutability is "practically immutable" by making member variables and any methods const.
struct RockSolid {
const float x;
const float y;
float MakeHarderConcrete() const { return x + y; }
}
Is this actually the way "we should do it" in C++? Or is there a better way?
The way you proposed is perfectly fine, except if in your code you need to make assignment of RockSolid variables, like this:
RockSolid a(0,1);
RockSolid b(0,1);
a = b;
This would not work as the copy assignment operator would have been deleted by the compiler.
So an alternative is to rewrite your struct as a class with private data members, and only public const functions.
class RockSolid {
private:
float x;
float y;
public:
RockSolid(float _x, float _y) : x(_x), y(_y) {
}
float MakeHarderConcrete() const { return x + y; }
float getX() const { return x; }
float getY() const { return y; }
}
In this way, your RockSolid objects are (pseudo-)immutables, but you are still able to make assignments.