I know references are syntactic sugar, so code is easier to read and write.
But what are the differences?
Summary from answers and links below:
- A pointer can be re-assigned any number of times while a reference can not be re-seated after binding.
- Pointers can point nowhere (
NULL), whereas reference always refer to an object.
- You can't take the address of a reference like you can with pointers.
- There's no "reference arithmetics" (but you can take the address of an object pointed by a reference and do pointer arithmetics on it as in
&obj + 5).
To clarify a misconception:
The C++ standard is very careful to avoid dictating how a compiler must implement references, but every C++ compiler implements references as pointers. That is, a declaration such as:
int &ri = i;
if it's not optimized away entirely, allocates the same amount of storage as a pointer, and places the address of i into that storage.
So, a pointer and a reference both occupy the same amount of memory.
As a general rule,
- Use references in function parameters and return types to define useful and self-documenting interfaces.
- Use pointers to implement algorithms and data structures.