Learn Rust

Cargo

Cargo is tool for Rust providing:

• Dependency management: declare and manage dependencies.
• Build System:
  • Build dependencies, compile, linking, generation and running of output binary or library. (cargo build and/or cargo run)
  • Test runner (cargo test)
  • Project setup (cargo new)
  • Documentation generation (cargo doc)

Cargo.toml

Cargo.toml defines your app config.

The 1.0/hello_world has 2 tables:

• [package]: metadata about the project
• [[bin]]: specifies our target (e.g. binary but could be [lib] for a library.

Using Cargo

• $ cargo build && $ ./target/debug/filename (manual run step)
• $ cargo run (build and run)

Rust Lang 101

See book/1.0/basics/basics.rs for code examples. See README_TYPES.md for type examples.

• Immutable bindings by default. Can mutate bindings if mut is specified.
• Strong typing doesn't automatically turn one type into another
• Static typing knows what type elements are before program runs
• Implicit typing compilier can often infer binding types
• Ownership and Borrowing
  • A variable has ownership of resource they are bound to.
  • When binding is out of scope the resource is freed.
  • Only have 1 binding to a resource at any 1 time.
  • How do we work with our resources? Some options:
    • Move
      • We can move values from one binding to another e.g. we re-assign binding (new binding takes ownership) or pass a binding to a function (function takes ownership)
    • Copy
      • If the resource is Copy (implements the Copy trait) this allows the resource to be copied instead of moving it to another binding.
    • Borrow
      • Borrow cannot last longer than owner scope.
      • Borrow ends when borrower goes out of scope.
      • Only one type of borrow at a time, either:
        • n Reader Borrows - give n number of references (&T) to a resource.
        • 1 Write Borrow - give exactly 1 mutable reference (&mut T) to a resource. Prevents data races.
• Traits - similar to interfaces, they define a set of methods that a type must implement in order to be that trait. Trait methods can then be implmemented by your own types. You can also generate default implementation of traits e.g. using #[derive(Copy)] above a type where possible.
• Lifetimes - ensures that references do not point to a resource that has been deallocated from memory (dangling pointer). Every reference has a automatic lifetime but sometimes it must be explicitly specified. Needed when using structs and impl blocks. Lifetimes can be re-used between variables. You can think about lifetimes purely in terms of scopes but naming them allows referring to each variable scope by name.
• Imports - packages imported using use some::module::path. Some std library packages are included automatically e.g. Vec is, LinkedList is not.

### Sources

• https://www.udemy.com/course/rust-building-reusable-code-with-rust-from-scratch
• Rust Book: https://doc.rust-lang.org/book/