Question

I’m reading Essential C++. In the section 4.3, the author gives an example to
explain the usage of const

class val_class {
public:
    val_class(const BigClass &v)
        : _val(v) {}

    const BigClass& val() const {return _val;}
    BigClass& val() {return _val;}
};

void example(const BigClass *pbc, BigClass &rbc)
{
    pbc->val();
    rbc.val();
}

In the above code segment, the author overloads the function val based on constness.
And then the pbc->val() will invoke const instance, rbc.val() will invoke non-const instance.

The pbc is a const pointer of type BigClass. How can we guarantee that the BigClass has a member function val ? Should the BigClass be replaced with val_class in the example function?

Answer 1

Must be this: Your Full Example

This is obviously just a typo in the book. As you figured out for yourself, the example function should look as follows

void example(const val_class *pbc, val_class &rbc)
{
    pbc->val();
    rbc.val();
}