C++ equivalent of algebraic datatype?

Let's say I have this Haskell code:

data RigidBody = RigidBody Vector3 Vector3 Float Shape -- position, velocity, mass and shape
data Shape = Ball Float -- radius
           | ConvexPolygon [Triangle]

What would be the best way to express this in C++?

struct Rigid_body {
    glm::vec3 position;
    glm::vec3 velocity;
    float mass;
    *???* shape;
};

The thing I'm asking is how to represent shape inside the struct when it can be one of two types.