Brownian Bridge™

1. You have an abstract base class `Model` with a `virtual Model* clone() const = 0;` method. A `PathSimulator` stores `const Model* _model`. In the `PathSimulator` copy constructor, which of the following correctly performs a deep copy of the model?

`_model = other._model;``_model = new Model(*other._model);``_model = other._model->clone();``_model = static_cast<Model*>(other._model);`

2. The following code compiles successfully: ```cpp Distribution d("base"); // Distribution has a pure virtual pdf() d.cdf(0.5); // cdf() is non-virtual ```

truefalse

3. What is **object slicing** in the context of a `Distribution` hierarchy?

Calling `delete` on a derived pointer through a base pointer without a virtual destructorCopying a `NormalDistribution` object into a `Distribution` variable by value — the `_mean` and `_variance` members are discardedSplitting the object across two cache lines, causing a performance penaltyPartial initialisation of derived members when the base constructor throws

4. The `clone()` method returns `NormalDistribution*` (not `Distribution*`) in the `NormalDistribution` override. This is called a **covariant return type**. What is the primary benefit?

It avoids the virtual dispatch overheadA caller holding a `NormalDistribution*` receives a `NormalDistribution*` without a cast; a caller holding a `Distribution*` receives a `Distribution*` — the correct derived type is returned in both casesIt allows the compiler to inline the clone callIt prevents the base class from being instantiated

5. If `Distribution` has a `virtual ~Distribution() = default;` destructor, then `delete d_ptr;` where `d_ptr` is a `Distribution*` pointing to a `NormalDistribution` object will correctly invoke `NormalDistribution`'s destructor.

truefalse

6. In the copy assignment operator for `NormalDistribution`, why must you call `Distribution::operator=(other)` explicitly?

To avoid infinite recursionTo copy the `_name` member defined in the base class, which `NormalDistribution::operator=` cannot access directly if it is `protected`Because base class assignment operators are never inheritedTo trigger the virtual dispatch mechanism for assignment

Quiz: Abstract Classes and the Clone Pattern

Quick Quiz