pelicin › prog › C++

References

References are "safer, more convenient" versions of pointers (Lospinoso). A reference is an alias for an existing object (learncpp.com).

You cannot reassign a reference. (Trying to assign to a reference will change the referenced object's value instead.)

Defining a reference

Append & after the type, e.g. int&. You always have to initialize a reference.

int my_number = 123;
int& my_ref = my_number;

Dealing with references

As lvalue

When they appear on the left side of an assignment expression (except during initialization), you are changing the referenced object's value.

Syntactically, assign to the them the referenced object's value.

int my_number = 123;
int& my_ref = my_number;

printf("%d\n", my_number); //=> 123
printf("%d\n", my_ref); //=> 123

// Assigning to a reference means
// assigning the referenced object's value
my_ref = 456;
printf("%d\n", my_number); //=> 456
printf("%d\n", my_ref); //=> 456

Again, assign to them the referenced object's value.

int my_number = 123;
int* my_ptr = &my_number;

// Syntactically, assign to `my_ref` a "value"
// (they still store the address of `my_num«ber`, though)
int& my_ref = *my_ptr;

// Trying to do any of these yield a compile error:
// - int& my_ref = &my_number; (trying to assign int* to an int reference)
// - int& my_ref = &my_ptr; (trying to assign int** to an int reference)

As rvalue

When they appear on the right side of an assignment expression (except during initialization), you are copying the referenced object's value (NOT the address).

int a = 123;
int& a_ref = a;

// `b` is assigned with the referenced VALUE of `a_ref`
// (changing `b` will not change `a`)
int b = a_ref;
b = 456;

printf("%d\n", a); //=> 123
printf("%d\n", b); //=> 456

References