I came from C++, and try to understand what Rust reference is. According to my current understanding, I think Rust reference is more close to C++ pointer, is that right?
You can see:
&T can be converted into const T* safely
Trying to modify the value of a binding through a mut ref, you need to write:
let mut a=1;
let b = &mut a;
*b = 5;
i.e., use * to convert a reference to a value (which is same for pointer in C++).
In Rust, a reference...
Must point to something and is implicitly dereferenced on method calls and data member access (like a C++ reference)
Can be reassigned and must be explicitly dereferenced with
*
for value mutation (like a C++ pointer)
Must obey ownership and borrowing rules (unlike any form of C++ indirection)
Thus, my answer would be "it's a bit of both, and then some".
I think that Rust references are in the middle between C++ pointers and references.
Pointer like traits:
It's possible to rebind a rust reference
fn main() {
let mut i32_ref: &i32 = &92;
eprintln!("i32_ref = {:?}", i32_ref);
i32_ref = &62;
eprintln!("i32_ref = {:?}", i32_ref);
Explicit deference (*) and borrow (&) operations are required.
Reference like traits:
Never null.
No need for -> operator.
No intrinsic numerical value.
Unique traits:
ownership and borrowing
sizeof rust reference can be twice that of a pointer (for slices and trait objects)
Probably the closes thing to Rust references in C++ is reference_wrapper?
Forget about comparing references to pointers. It will make you struggle with the borrow checker.
Think of Rust references as read/write locks for objects in memory that give a temporary permission to access something.
In C it's usual to use lots of pointers for basically anything, but in Rust using many references may get quite cumbersome or not even pass the borrow checker.
In C it's normal to allocate and return something as a pointer, but in Rust that kind of pointer doesn't even have a syntax! For example, Box is a pointer, and Rc, String and Vec are used in the same places where you'd use a pointer in C, despite being neither a pointer nor a reference.
