Intro to Rust

Why Rust (from a memory perspective) #

What makes good code?

  • Pre/post conditions to break code into small pieces with well-defined interfaces in between
    • Want to reason about small pieces in isolation
    • If pre/post conditions of each piece is held up in isolation, then simply stringing them together works without having to keep entirety of program in one’s head
  • Code with good memory management clearly defines how memory is passed around and “who” is responsible for cleaning it up

C/C++’s compiler cannot effectively verify pre/post conditions with regards to memory. Rust’s does.

Memory ownership #

Rules #

  • Each value in Rust has a variable that is its owner
  • There can be only one owner at a time
  • When the owner goes out of scope, the value gets dropped

These rules are enforced at compile time!

Basic example #

fn main() {
    let a = Bear::get();

a is the owner of the string and can do anything with it (ex. use member functions), and is responsible for freeing the memory.

fn main() {
    let a = Bear::get();
    let b = a;

Now, b is the owner and has the same access privileges and responsibility; whereas a relinquishes all privileges and responsibilities.

Borrowing #

fn main() {
    let a = Bear::get();
    /* a still has ownership and still can be used */

my_cool_bear_function borrows the bear, but eventually gives it back to a, at which point a is responsible for freeing it.